My desires aren't very original...just want to chime in with others.
We were in a regular F suite for the entire 2007 and found the space more than adequate (though we weren't big shoppers).
We sent six pieces of luggage to the ship and brought airline luggage with us. The closet space was adequate. Though we did store some things like sweaters or extra clothes in a an open suitcase or two under the bed, we still managed to have one empty drawer thorughout the trip.
I don't believe the normal suites need to be any bigger. If the beam of the ship is wider, I would add the space to the depth of the balcony.
Keep all it an all-balcony ship. Stay with the single hallway...so that you have neighbors across the way.
The Voyager-size baths, including the size of the shower stall, are more than adequate.
A little larger exercise room with additonal treadmills and stationary bikes would help.
Agree that a complete, somewhat-protected, prommenade deck would be a tremendous iimprovement -- for those who like to walk, but don't enjoy fighting the wind!
750 pax would be OK...but wouldn't want it much bigger.