My problem is with logical consistency
What's the problem with a "mobile" aegis attached to a ship?
I've tried to ask this a couple of times, and I just fail to see any answer.
Particularly given that a ship, or a flotilla of ships, is a "common" site for Covenants.
I mean: look at Covenants, p.9 the Major Site Hook
Constantly Mobile: This covenant moves constantly. For example, the Covenant of Crisp Winds lives on a flotilla of ships, which follows a route around the Mediterranean to collect vis and trade goods at auspicious times. If the covenant were to cease moving, it would lose its income."
The problem is that the aegis is defined to be non-mobile and that is an aspect of the game which is desired to be retained.
It seems to me the entire idea of wards being type 1 that act upon the space inside exists entirely to make the aegis non-mobile, so it makes sense to find a simpler solution to that dilemma
There is also the issue of what happens when a mobile aegis runs into something magical...
Well, we've definitely reached the point of me not caring about the outcome of the discussion because I'm going to ignore LoH and continue to permit mobile Aegis and other wards whether it's a house rule or not. Too much cool stuff depends on it, and too much weird counterintuitive bull follows from the reverse.
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The fundamental problem is, I think, mobile relative to what?
The Aegis should arguably be immobile relative to the boundary it wards, i.e. to its immediate environment. So if that immediate environment mvoes - e.g. because your covenant is on an island, and the entire island moves, the Aegis should stay attached to the covenant, not wander around the island as the island wanders around relative to absolute space.
And frankly whiy should a "conventionally mobile" covenant site have no Aegis, but one that bases its mobility on "space warping" (a regio that opens portals all over Mythic Europe) should have it? I do not think I am the only one to see this as problematic.
There are multiple aspects to this, but to me the primary issue seems to be that David Chart is looking specifically for a solution which keeps the aegis immobile. Personally I'd be willing to figure out collision rules for mobile aegis', but since that does not seem to be where things are headed I don't see a point n working that out at this point.
And of course there are always breakthroughs...
Sure. I am just questioning the frame of reference in which the Aegis (and Wards in general) should be immobile.
I think immobile relative to the immediate environment - as conveniently defined by the Target Boundary - is simpler, more faithful to folklore, and more saga-enabling, than immobile relative to "absolute space". The latter seems a good possiblity for a breakthrough, though 
Anyway, I've stated my point (over)abundantly, I think. I rest my case.
And my point is that when you have a covenant on a cloud and a covenant on a mobile island and they each have an aegis then you have to answer what happens when the cloud passes over the island. Not something that can't be done, obviously, but there are reasons beyond the fact that the immobility of the company policy on these issues.
There is arguably two cases bring weird results:
*Flying ships that are warded by an Aegis, flying through or landing in another Aegis;
*Flying warding ring talismans.
Mind you, I think I still prefer the issues of an Aegis-warded flying vehicle entering an Aegis static area to the issues that are generated by moving a covenant out of its own aegis through moving the landscape on which the covenant is built, but that's me.
I also have no idea what the rules about non-moving would mean for regios that are connected to a mobile spot.
And was so already on ArM5 p.114 Magical Wards. No changes in MR are implied by it.
Mice (by A&A p.30f Worms) are born of damp earth in your cabin. No need to ward against them: you need to kill them anyway day-after-day by magic. 
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EDIT: Withdrawn, already covered by @OneShot above.
Note I wrote Lice, not Mice
But you made a good point for allowing seafaring magi to ward their cabins against dampness
This seems no problem at all to me with a "type 2" Aegis (that is immobile in its Boundary's frame of reference, i.e. that "follows" its Boundary).
I assume that the flying ship either lands or flies low enough to enter the island's own Boundary; otherwise there is no problem, as the two Boundaries remain separate. I also assume that the Boundaries remain substantially intact: if the flying ship crashes, it ceases to be a Boundary, so again there is no problem.
Then, as the flying ship enchantments (including the flying ship's own Aegis) enter the island's Aegis, the normal Aegis rules apply to them: assuming they are "foreign" the island's Aegis resists them, and they fizzle out if they fail to penetrate (note that the reverse does not apply: it's the ship's Boundary and Aegis that entered the island's, not the other way round). If the ship's Aegis fizzles out, case solved.
If not, we have two concentric Boundaries, protected by two Aegis, exactly as if the first Aegis had been cast on the island's Boundary first, and the second Aegis had been successfully cast on the ship's Boundary next. Everything is resolved as normal.
Where's the problem? I really don't see it.
Uh? Can you make a more specific, concrete example?
Oh no, it's not just you. I myself find that just soo dissonant with the mythic paradigm. Pulling the proverbial rug under a covenant's feet, as it were.
I suspect the handwavy explanation would be along the lines: the regio is nowhere (or alternatively, elsewhere), so it does not move; it's just the entry point that moves. Which irks me, because it means that the Semita Errabunda way is the only way that most people will want to have a mobile covenant under the current propsal.
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My imperfect musings on the subject:
If the Earth is immobile, and the Aegis' duration is determined by the cycle of the heavens, then the Aegis' location at the time of casting must be fixed for the duration of the spell to remain valid, otherwise you would change the time of its expiry.
Thus the Aegis is immobile not just due to Boundary target, but also due to its Year duration. This might be true for all Boundary, non-concentration spells. A moving island doesn't violate the Boundary condition, but it does violate the Year duration conditions due to changing positions relative to its heavenly defined Duration.
Note that other spells are not so closely tied to position beneath the heavens (even a structure can be defined as mobile), so are more loosely tied to their heavenly duration.
Note: I actually don't have much of a problem with a mobile Aegis, as it makes ship-borne covenants more possible, as well as flying castles, mobile islands, even covenants that shift through regiones. But if you want Boundaries to be immobile in most cases, their position under heaven is a good reason, as it can easily be part of the definition of Boundary as well as under-writing its Duration.
Iām not sure I believe that Diameter, Sun, and Moon durations are any less linked to the movement of their respective celestial bodies. Based in that reasoning, if one could move fast enough it should be possible to keep a Sun duration spell active forever by following the sun around the earth and never letting it hit sunrise/sunset at your current location.
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That's why I mentioned Concentration based spells, which are the only ones that have a duration that's not celestially bound (Ok Ring duration too). A Sun/Boundary spell would be similarly immobile. And note that Sun spells in the far north can last for months because the sun doesn't set, IIRC this is covered in the Hyperborea section of Ancient Magic and maybe in Ultima Thule?