Just some ideas I've had since starting the thread:

The Cerberus could easily be used as inspiration for a new t5 Starcruiser, as well as t4 and both t5 science configurations (I just love the Cerberus nacelles; they should use em more ).

If the Nebula is ever added to the game, I think every ship in that configuration should be based on something else (say 1 other from t4 cruisers, and 1 from t5 Assault cruisers). After all, the Nebula was a smaller counterpart to the Galaxy, the others should fill the same role for other starship generations.

A t3 Akira config escort based on the 'Cryptic's own' starter ship (not the Miranda or Centaur, the other one... I just can't remember the name ).

A Galaxy styled t5 Advanced escort based loosely on the Challenger could work (could even say it's a refit or something).