I agree a theme might be useful. Doesn't have to be a straitjacket, but a theme nevertheless. So this is some kind of brainstorming/theme finding thread:
To me Rome/Italy is defined by:
Demons, demons everywhere!
Sorry, assumed you wanted to stay conceptually faithful to the original. 
Hm... Perhaps a more in-depth look at the culture, tradition, and societal standards of the area, especially what sorts of supernatural creatures might be prevalent. Local (peasants!) story hooks, of course, but those were almost certain to be included anyway.
Lets see,
I would suggest a theme about the a Search for the Spirit of the Antiquity:
The Order could be organized
A few things:
The problem with the organization in the Roman way is that the real power of the order lies in the Rhine. The Roman tribunal may well be in a sort of unstated denial about this, but I don't think we need another tribunal with a radically divergent means of organization.
One thing which just occurred to me is going round and round in all of this is the winter-spring boundary- old things falling apart as new things rise. The old power structure of Italy is about to be challenged by Fredrick II, the renaissance is just beginning to start due to books and ideas from the Levant as the crusades fall apart following the 4th, the number of ways that creo and perdo intertwine here really do seem to create a natural theme.
Ruins and Reawakening.
si tacuisses philosophus mansisses 
There is more than one volcano in Italy!
nice
Not bad. The only issue I have with this that it is only usable for players who have all the sourcebooks. There should be at least a part of the project that is playable with the core and HoH books.
nicely put
The thing with the Augustinian Brotherhood is that we don't want to overplay it (the tribunal should be playable without involving them) but we certainly can't let them go unmentioned either. Similarly we should at least mention the degree of hedge traditions (and perhaps that there are many more than are in the book), perhaps with the implicit suggestion that many of these may be on their last legs, and more may be just starting if we keep with the theme.
I just read through the mundane and hermetic history sections of the Rome book during the last few hours. For the first time ever mind you.
My main concerns are how the Order works in this tribunal and the overall theme, because they influence what covenants to put in the tribunal. Each of them should serve some purpose to further stories and underline the concept.
I seem to do my best thinking while I'm writing, so this posting has been re-written to reflect my best ideas rather than be a long list of speculations.
I see the Roman Tribunal in Hermetic society as a reflection of mundane society. Enduring conflicts and power struggles both internally (in covenants, like in city states) and externally (between city states). The disappearing Magical and Faerie auras and vis makes sense, following the spread of mundane activity and influence of the Church. This lack of resources has caused a recession in Hermetic society for centuries, relatively few covenants exist and all of them old. Newer covenants never make it for long before succumbing to hostile action from the older, powerful covenants. A peripheral code exists to try and limit mundane meddling, but it leaves many openings especially when using mundane intermediaries. It also gives more power to older magi (somehow?) and effectively blocks new covenants forming. What few resources exist are fought over. But instead of disappearing completely it has recently been discovered that the Dominion merely suppresses and hides resources previously believed to have been lost.
Like the Guelphs and Ghibbelines fight for control over city states, magi fight for control of their covenant. Like whichever family is dominant decides on the politics of the city state, the dominant faction of magi rule the covenant at a given time. But this is likely to change back and forth again and again. Magi form alliances in their Hermetic lineage, with sodales from their house, and may even ally with another house's lineage with common goals. Magi are split into two dominant factions; One group deeply involved with the Church, uses plotting, intrigue, diplomacy, blackmail bribe, and whatever subterfuge is needed to consolidate power and holdings with the blessing of the Church as well as getting concessions to procure vis previously hidden or unavailable. The other faction is more aggressive and sides with the merchant-princes and warring nobles, involve themselves in conquest and crusades to raid what magical resources and profit they can get away with.
But with all the covenants being old they also grow stale and dominated by one of two factions led by old magi too deeply scarred by history and bad blood to rule in a constructive manner. New generations of magi try to break free from this stranglehold, to stem the violence and plotting and to stop the decay. They want to the rebirth of the whole tribunal by allowing a seed to grow to a fresh new sapling from the toppled, rotting tree from where it came. They want to look outwards again, to explore and perhaps colonize Africa. Not that the factionalizing and plotting is likely to stop immediately, it will be an ongoing process.
So for a saga to start out the classic Spring start and build-your-own-covenant is different than usual, because if you don't also have the older covenants undergo a generational change they would squash the newcomers. But a Second Spring start in an old covenant is also an option.
So, I have here the (apparent) loss of resources which causes power struggles, but with a (sort of ) solution as to why the magi haven't died out or moved on. I have plotting and power struggles involving the Church as well as city states, to mirror the mundane society. Sure, there may be corruption and infernalism, but I'd prefer if it wasn't dominant. It's ok to be gritty and dark, but I'd rather have paranoia about these kinds of things than having it be the norm. Sometimes it's not a demon but a dark hedge wizard or cult. Also, I have the Ruin and Reawakening with the way things are about to change.
@Christian: I love it.
One thought to add. I agree there will be little vis, but there probably lots of books.
I like the "ruins and reawakening" suggestion, though I'd like pose an idea before that gets taken up too strongly. Consider why anyone would play in the Roman Tribunal. What would sagas set using the Roman Tribunal tend to look for, and that is different from the other Tribunals? (Edit: Christian wrote some similar things above.) Three things pop into my head quickly:
Those both seem somewhat like the Rhine Tribunal, but the type of interactions would likely be very different since the Roman Tribunal is more on the mercantile end (Verditius, Mercere) versus the historical political end of the Rhine (Bonisagus).
That leads to me liking the "ruins and reawakening" suggestion. It suggests so much that is there and that if it's being played people are revitalizing covenants or looking for things that were lost.
I'm kind of torn about pitching in for this. One the one hand, I very nearly sent David a speculative pitch for the Tribunal a while back and I have a rough vision of the Tribunal kind of worked out. On the other hand, I don't want to constrain the forum creativity that this project is going to set free.
But if it's of any value, here's the very short version of the pitch (which ignores the crunchy Sicily stuff for brevity).
The Hermetic Roman Tribunal reflects the city states that are rising to prominence across the peninsula. Smaller covenants have come together, some bowing under pressure of their more powerful neighbours, others aligning through convenience. The boundaries of these new covenants are now recognised to follow the boundaries of the mundane city states.
While the dominion is strong across the Tribunal, the covenants use their agents to protect their interests, particularly the magical and faerie resources that are so valuable. The magi of the Order have become patrons; patrons to political families, to mercenary generals, to artists, to practitioners of hedge magic, and to universities.
Behind the accord, that acceptance of rights and boundaries, there is intrigue. Resources are not as scarce as some might have you believe, but they are jealously guarded and form valuable trade between covenants. And so Hermetic patrons may influence their charges to acquire, by force or purchase, those lands which extend their rights and influence.
The game is a political one and its victims are the unwitting mundanes who act upon their unknown masters' orders.
The only thing I would have as an issue with that 'pitch' is that in 1220 the politics and intrigue, at least on the mundane side, is starting to boil over into military action. Sicily already allows Malta to conduct raids on Venetian ships, and Fredrick II is about to promote the Count of Malta (who is a well known pirate attacking Siciliian merchants) to head of his Navy, while the failure of the 5th crusade is about to start the slow burn that turns the relationship between the Pope and Fredrick II from allies to bitter enemies. Meanwhile the Lombardy league is trying to establish their independence and it seems like the harder they try the more Fredrick II and the Pope want them crushed... and war is very much on the horizon. Is the order going to be at war with itself as well, or do we allow the order to stand strong and let it play with external enemies in a shadow war of intrigue which may yet open up into hostilities?
As I said, the very short pitch.
Or, if we combine silveroak's comment with marklawford's, we see Mark's last line really ringing true. Sounds somewhat like the Soviet Union and the United States of America never going to war but investing heavily in conflicts against the other (Korea, Vietnam, Afghanistan, etc.). Maybe part of the reason there is so much mundane military action and raiding is that the Hermetic magi are pushing the lords who control areas of their interest to expand so that the magi control greater resources, too. The result is the "victims are the unwitting mundanes who act upon their unkown masters' orders."
That could happen, but a proxy war within the order is still a war within the order, and one which should get the quaesitors involved very quickly unless the tribunal has hit a level of corruption which far exceeds that in the third edition. There is also the question of how they push things this far despite the social penalty of the gift without causing mundane repurcussions. Plus the Augustinian Brotherhood's involvement is already cannon- I would rather the order be fighting cloak and dagger intrigue with 'unknowns' than see it ripped apart from within- after all what we are seeing in Italy is not it being torn apart from within but different forces from different areas- the Papacy on one hand the remains of the Byzantine empire's attempt at influence with the Lombard League, the Franks in the form of Fredrick II... this isn't small internal issues tearing Italy apart but large external ones.
@Pralix:
Thanks. And yes, with little vis in circulation books are likely to be more common, perhaps even to the degree that tractatus are used as currency
@callen:
Yes, with few wild and unexplored places it's more about re-finding things that are lost, like Ancient Magic-style lost traditions, cult and magics. Magic that can be integrated into Hermetic theory
@Mark Lawford
Interesting pitch. So the magi use and manipulate powerful mundanes to push for more power and conquer the resources of their enemies? It's not completely contrary to my ideas. I just have internal struggles within the covenants as well, where one faction may be manipulating certain powerful families in city states, while the other is working the system at papal court. Just like the city states the covenants dominate may experience fluctuations in power, changing which family is effectively in charge
@Silveroak
Just because one covenant is warring by proxy with another covenant doesn't mean the fabric of Hermetic society is breaking down. Wizard's War is a legitimate conflict, and Hibernia has lots of fighting going on. Sure, if you lose vis sources from your locale because the neighboring city-state conquers the lands, and a rival covenant is behind it, it could be a case of Deprivation of magical Resources. So you take the matter to Tribunal, but you might lack support because you in fact were a complete douche to a third covenant so they side with your enemy (for now).
Also, the Augustean Brotherhood could easily be a faction which some covenants engage in a proxy war against.
It's all about the different play style with me. We did Hibernia where the conflict was clearly and overtly magus vs. magus and I wanted something a little more political and distanced for Rome. Not to say that magi disappear from the game (they don't) but I envisioned companion characters and agents being really important for this Tribunal.
I never fully developed my overall pitch - I needed to put a team together to arrive at that - but I can well imagine content designed to foster rivalry between player magi. The awarding of grants and titles, competing for positions of influence within the covenant, perhaps based on a common charter imposed by Magvillus and ratified by the Tribunal years ago to head off growing conflict.
See, it's all a bit nebulous. I'd kind of thought about lots of little bits but never really pulled it together. Verdi would have been spoiling for a fight with Ingasia over in Thebes though, of that I'm certain.
I should add... At this point, I'm done.