I would love to play as Xemnas, though all I'd be doing is staring at Kingdom Hearts, talking to Aqua's armor, and watching everyone sleep. I was disappointed I couldn't do more as Roxas in Days.
For example, exploring the castle. It would have been fun going to everyone's rooms, looking around, but when I exited said member would appear behind me, scold me, then send me to the Grey Area and I'd have to do a mission while locked out of the bedroom area. Or heck, explore my own room. I know it's barren, but I'd at least like to wake up and find a gift someone left on my dresser or have an extra inventory in my room.