What I would adore is some kinda small faction neutral ship. With one less boff slot than other VA ships but they're all universal. So you've got one commander slot, one lt cmdr slot one lt slot and one ensign slot. Or maybe just one commander and two lt cmdr.
Its stats change depending on which kind of boff is in the commander slot.
If a tac then the ship handles more like an escort with the associated weapon power buff.
If an engineer then it handles like a cruiser with the shield capacity buffs and shield power buff you'd expect from one.
If a science boff then it gains subsystem targetting and an aux power buff.
It would create an obscenely versatile ship but one that has a harder time filling any specific role.