The principal users of civil airports & GAT airspace are the ME fleet
GAT is routinely used by FJs on ops; I’ve many hours up and down the Gulf working Bahrain, Kuwait etc out of the ‘Deid on Op TELIC. And it’s GAT for all players out of Akrotiri at the moment as well. It’s very often easier than OAT when overseas.
FJs don’t often land at civil airports but often hold them as diversions, so they will need to keep pace with these changes somehow. Especially at home, where the MOD seems bent on reducing the number of military airfields available for diversion.
A fly in the RNP ointment is jamming of GPS and DME transponder frequencies; military aircraft don’t have the easy civil get-out of not operating under such conditions. Alternatives will need to exist and will take up the precious avionic space that might otherwise be given over to triple-redundant IRUs with independent GPS. Copying the civil world doesn’t answer all our problems, I’m afraid, and military get-out clauses exist for that precise reason.