I'd love a sequel for Ghost Trick, but Capcom and it's incompetent marketing team dropped the ball HARD with Ghost Trick and made that highly unlikely.
I suppose I would want them to build upon the formula they created, since as it stands it's a fairly thin game, which is fine because the focus was clearly put on the storytelling and audiovisuals and it does those exceptionally well, but it could have been so much more. As it stands, the whole game is just waiting for paths to open up and triggering animations, and while they tried to mix up thing by introducing an item swapping mechanic, it really wasn't enough variety for a game of this length.
So, I'd like to see more mechanics introduced to make puzzles more complex and less linear, as well as having some simulation elements to it, kind like The Incredible Machine, instead of just relying exclusively on pre-animated events.