I'm hoping for a slight turn rate improvement, but perhaps the saucer separation will cover that need. Personally I prefer keeping my ships whole because I feel they look better that way... but maybe I'll like the Odyssey's star drive look.
Boff improvement of the kind of improving the Ensign_Science to Ensign_Universal could be nice... but I'm okay working with what we have right now.
If saucer separation and the auxiliary craft combat pet come with consoles, I'm hoping to see some degree of console expansion to compensate. Ideally, I figure a +1 bump to either science or tactical slots (I can work with either), the aux craft as a console, and the saucer separation as a ship-innate power could be nice.
Most especially, though: I want the Auxiliary craft (the Sacagewea?) to be playable like the D'Kyr's aux craft was. If it's a shuttle, that'd be awesome and could work in shuttle mission. If it's a small escort viable for Tier 5 play, I'll also be very happy and gladly switch from the Defiant to it - I really like it.