Here's a fun alternative:
One thing that's missing from the TNG/DS9 era is a cruiser-starship like Kirk's original Enterprise. Of course, the term "heavy cruiser" changed its meaning significantly in a hundred years, but I think it would be interesting to take this saucer idea in the opposite direction, and take the secondary hull from a Sovereign-class starship, trim it down a little, give it a smaller saucer, so that the ship has a crew of 400-500. (Call it Sovereign lite, if you like) This ship would be larger than Voyager, but smaller and simpler than Sovereign or Nebula or Galaxy. It would be built for limited deep space exploration (like Kirk's Enterprise) and could also be used for combat.
Now, here's a new possibility: give it the capacity to dock one or two Defiant-class escorts on the outer hull, maybe down where that cavity that's on the aft-keel of the secondary hull. Essentially, most of the design work for the Sovereign-class has already been done for this new class of "lite" cruiser (probably sized between the Enterprise-A and -B) and most of the Sovereign components (nacelles, secondary hull pieces) can be used for economies of scale. I wouldn't be surprised if the manpower, raw materials, and energy needed to build a Sovereign or Galaxy could be just as easily redirected to build a "lite" ship and maybe a Defiant or two. If you're wanting more defensive/offensive capability and still retain non-military flexibility, that would seem to be the ticket.
I'm not sure if the fan-made Posiedon
would fit that bill, but from the looks of it, it sure seems to come close.