Air is still matter, not void, in both Platonic and Aristotelian cosmology. See A&A p.22.
So you need to do a lot more than handwaving to prevent air from forming an area delimited by an ArM5 p.113 T: Boundary.
The spell affects everything within a well-defined natural or man-made boundary.
If you allow the boundary to move, what it contains and defines is changing.
Aegis affects a Boundary. So in order for Unraveling to affect it, it must affect the entire Boundary, therefore, it affects an area.
You might not like this reading of the rules, but you dismiss it as if it can't happen, and this after saying that I am not being serious here.
AotH is a spell. What it affects - area, group or whatever - is for UtFo(F) irrelevant, as long as it is a single spell. You quoted that yourself above.
Standard is instant transportation, sure. That is not the same as it taking no time at all.
The word "instant" is used about many things in the real world. Not a single one of them takes no time at all - they all take some time, even if it is a very, very, very short time. Why would the word mean something different in Ars Magica?
I am going to come out and say that I am both strongly in favor of errata requiring a "Ritual to be used to dispel a ritual" and official clarification on if an Individual Target spell is enough to dispel a spell covering a large area. The back and forth will not accomplish anything since both sides are dug in. Personally I would rather that something make dispelling a Ritual more difficult.
In the description of the Boundary target, all of the given examples are of boundaries that cannot be arbitrarily changed the way a loop of rope could be. It also says, "Since the ocean is not obviously bounded, it cannot be affected in this way." So, I would say that a Boundary is intrinsic to the thing that is being bounded. In order to move the boundary of a town, you must move the town. Therefore, an Aegis, when cast, is cast upon a specific thing (town, lake, forest, mountain, covenant, etc.) which cannot arbitrarily change for that Aegis.
So, an Aegis cast upon a ship, using the clear boundary between ship and not-ship, has no problem moving with the ship (assuming for argument's sake that such a ruling has been made) as the boundary and the protected thing remain the same wherever the ship goes.
However, the rope looped around a portion of a field of grass doesn't work for two reasons. First, the rope is only dubiously a boundary for that portion of the field, as it is not an intrinsic boundary for that portion. More strongly, the thing that the Aegis protects is not "whatever is inside this loop of rope", but rather "this patch of grass that was defined by a loop of rope at time of casting". Further, I would argue that the patch of grass would lose its boundary and therefore its Aegis as soon as the loop of rope was moved--assuming the loop was allowed as a Boundary in the first place.
That may be a solution proposal.
To follow this up, redefine T: Boundary and replace in it:
The spell affects everything within a well-defined natural or man-made boundary.
Be careful here, as there are many spells you might affect and require erratas for.
The result may however also be a completely new T: Thing and a reworking of targets in general. Currently T: Boundary defines the Target by the boundary, not by any notion of thing. A rope, a chain, a path can as much define a T: Boundary as a coastline of an island, a wall of a town or the guard rail of a ship: it just needs to be well-defined.
After more thinking I reached more or less the same conclusion.
A movable boundary is fine, as long as that which is bounded moves with it.
A boundary that is movable relative to that which it bounds is not okay.
(Some flexibility should exist though - moving a boundary marker a few feet should not disrupt the whole boundary - but the exact limits should be up to each troupe.)
So a covenant on a ship, or a flying castle, or a floating island could all have an Aegis that moves with the covenant, but you can't put an Aegis on a portable fence to get an Aegis wherever you put the fence.
Do you say here, that nothing can be protected by an Aegis, unless it was protected by that Aegis when it was cast? Maybe with some exceptions for Aegis tokens?
That could help.
But you still have to define precisely, how a Boundary defines the Thing it is attached to and moves with.
@ErikT just said most of what I was going to say, and more succinctly that I would have.
I'll note that all of the examples in the target's description are things which are defined by their boundaries. Can anyone provide me with any Boundary spells that would have to be modified by ErikT's and my interpretation?
Lots of Aegides where the boundary is defined by the trail the magi use to walk around the covenant.
That does not satisfy boundary. There must be physical boundary markers such as a fence, edge of a forest, rivers, shore of a lake, standing stones, etc.
There is grey area when one considers where an un-walled town changes from town to not-town. I would say that the trail that the magi walk exists in such a grey area. That is, it's within the degree of flexibility that ErikT mentioned. After all, Boundary "cannot be used to simply affect a really big area", which I take to mean that you can't just walk any arbitrary path or just throw a hoop over some grass. There must be a covenant for the magi to walk around, and Boundary already places a limit on how far the magi may stray from the outermost covenant building, no matter how far they want to move their property markers.
In any case, It's still not a problem if one interprets T:Boundary to define the shape and extent of what is protected at the time of casting, and therefore what is protected for the duration of the spell. I see nothing in the description that contradicts that interpretation.
Which, unless it is a well-marked trail, is a bit at odds with the (current RAW) definition of T:Boundary which says "The spell affects everything within a well-defined natural or man-made boundary."
So you need to have something which one can point to and say "That is the boundary"
A marked trail does work. Just walking around the area without following an existing trail is not enough.
Why? The trail needs just to be recognizable at casting time.
Yes, this is also my understanding - and so far the Aegis is type 1. As long as the Aegis cannot be moved with a sofar unidentified "Thing", it works well. Once you wish to move it, you wish to define that "Thing" moving with the Aegis precisely. The boundary thus gets another, second purpose - or we get another type of Target.
That is not quite what I am saying, since that would mean that if you added another building in the middle of the covenant it would not be protected by the Aegis since it wasn't there when the Aegis was cast.
But if you just look at the area/volume protected by the Aegis rather than the specifics of what is in there then yeah, I suppose it would be implied by what I said.
What I am proposing is: For T:Boundary spells, the boundary can be moved if and only if that which it bounds moves with it.
I am thinking this should prevent your 'Aegis of assault' while allowing having an Aegis on a ship.
I went looking through my books - Favonius, the ship-based covenant of The Sundered Eagle, does not mention anything about whether it has an aegis or not.
Hermetic Projects - nothing in the Hermetic Shipyard section about putting Aegis on a boat. The Intangible Assassin section mentions a lot about Aegis and relation to wizard's war, and the spell Guttering of the home-fires (to suppress the Aegis) does not automatically need to be a ritual.
Does anyone have a copy of Legends of Hermes they could check to see if the flying castle mentions anything?
The "thing" is everything within the boundary at time of casting. I.e. the covenant and surrounding property as defined by its property markers, the town inside these walls, the field inside those fences, this small island, etc.
So if you land your assault ship with an Aegis and a hole in the middle around a wizard's tower, that wizard's tower can well end up in your Aegis and we are here again, so your Aegis can turn into a fully fledged Aegis of assault?