Pardon my proliferate number of posts 
I was brainstorming on a new Saga, and after having read The Contested Isle, I thought about the following.
What if a few of Connacht's Coill Trí druids got initiated into the Order, and worked together to use partly their own traditions' knowledge and that of the Order to establish the Coill Trí as a new house?
They would, I reckon, use the Coill Trí's contacts with the order to ask for having the Arts opened (Obviously having to be gifted), then undergo apprenticeship in Ex Miscellanea (probably) before being gauntleted as fullfledged magi.
Having their traditions still under their belt, they would conceivably not be particularly skilled magi – also because they might have lost some of the abilities when their Arts were opened. I imagine the players being the apprentices of these magi, so one link removed from the ”traditional” Coill Trí – fullfledged hermetic magi, but with heavy links to Connacht.
Also my idea would be that the Coill Trí druids in question agreeing to this endeavour would keep a very sharp focus – contacting the Order, asking for admission, getting it, and getting apprentices from Connacht where they would instill the traditional values into them and get them to dedicate themselves to the Coill Trí and its pursuit of formulating a unified lore based on the seven Túatha. ( It could even be a member of each Túatha or a handful of them who sought cross-Túatha cooperation on this)
Now of course there are, canon, some obstacles (Feel free to add more):
If the Coill Trí, or at least a few of its members, do have this idea, how do they go about returning to Connacht to establish a covenant? It is strictly forbidden - The Cnoc Maol Réid would have to be changed/adapted
Though entirely possible for Coill Trí druids to train as magi, how would the Order at large react to their ambitions? Now of course Hibernia being a rural backwater of sorts, and them possibly keeping their ambitions secret for a long time, they could organise quite a bit within their own ranks before starting to represent a unified whole – but at some point, if their ambitions carry forth, they would have to step out and say ”We are not ex Miscellanea, we petition to form House Coill Trí”
With the above in mind – such a house would lean relatively heavy on what is perceived as traditional druidic magic. Now with regards to Contested Isle we have descriptions of Diedne's progroms versus the Hibernian druids, so no love there – but would the rest of the order see this? Or would they just see ”F*ck the Diedne have risen again! March!”?
I definitely view this as the basis for an entire campaign, but also something which I feel should be doable – adapting and creating exactly the saga that YOU and your players want is a big part of any individual saga. And yes I know that I could just blatantly ignore and change facts, but I would love feedback rooted in canon.