At first glance, it makes sense (and more if you think that a turn is around 3-4 months).
I know the scrambling rules evolve from island only to all Air base, but it was always to protect a SZ.
AB were like a fixed carrier without the risk of exposing in a given SZ a 16 IPCs unit with a only a few escort ships.
Now, you are going in the other way, from SZ to land territory.
In certain way, it becomes like it was always forbidden since the beginning of A&A, providing a defensive air cover from an adjacent territory.
It gives a defensive boost without the risk of exposing vulnerable units such as fighters.
For sure, it is required that, as any other units on defense, no retreat is allowed for any incoming scrambled fighters.
And once the combat is over, contrary to the scramble rules, I will force the plane to land on this specific territory (no return to AB nor CV.)
If you allow Fg on a carrier from SZ to the bordering territory, would you allow a scramble in the adjacent SZ too?
If, yes it is like the carrier can defend all the SZs around the one he is effectively on.
Seems a big defensive cover when you have 3 CV and 6 Fgs.
The air cover of the CV will be like they were almost 3-5 place at the same time.
It becomes a complex matter for the attacker.
I would not allowed this for my part.
Only from SZ to adjacent ground territory.
(Just imagine it is harder to find the enemy in open ocean.)
I think it is probably this side effect of extended protection zone with carrier and ground territory around AB which make a problem. Usually there is up to 2 SZ, rarely 3 SZs around an AB, but sometimes there is up to 4 adjacent territories next to an airbase.
A weaker way to test this can be to limit this extension ground territory to 1 scrambled fighter only (per carrier and per AB).
It can be a way to play-test with less risk of creating an havoc and ruining the game your playing.
It would help you really figure out what happen and give some hints to why the rules never evolved in this direction.