In an interview with NGamer magazine, Tatsunoko vs. Capcom producer Ryota Niitsuma revealed that everyone's favorite defense attorney, Phoenix Wright, had been planned as a playable character in the crossover fighting game. Unfortunately, the team found difficulty in creating a moveset for Wright, due to his limited arsenal of combat techniques:
...because Phoenix Wright only has one move, 'Objection!', we struggled. We designed a move for him: when he says objection, the actual writing attacks the opponent. However, 'objection' in Japanese is 'igiari' -- it's four characters, whereas 'objection' becomes ten. When we localise, the balance of the game gets destroyed because the move becomes bigger. There'd be no way of avoiding it! We had to remove him for these reasons. In the future, it is one of our aims to get him in.
So, there's still hope that we may see Phoenix crop up in the future. What would be really awesome is if they decided to just make him a character unique to the North American release of the game. Only having him available in one special version of the game, the one that I will be buying and playing on my Wii, seems like a perfectly reasonable solution to me.