They could take the saucer section and "Defiant-ize" it a bit for an escort.
Wasn't the Luna designed from the ground up for its own type of mission? It serves a similar purpose, and is almost contemporary with the Enterprise-F, but it really is its own thing. It isn't quite as swoopy as the Ent-F, unless you use a Sol hull and nacelles (like I do). Also it doesn't have that catamaran look. That said, my Luna/Sol hybrid is currently my favorite ship in-game.