They can simply be called Galaxy Refit/Akira Refit etc.
Given the same number of slots and bonuses as the other classes. People can get the option to upgrade their already existing older ships with credits or merits maybe? Just like the galaxy refit in "All Good Things".
There are many ways to preserve the balance and oficer slot settings already put in place for Federation ships, along with making it possible to make use of older ships.
I'm dying to use the Galaxy class or the Sovereign for that matter.. the only reason i don't use them is because of the console/BO slots.