New Super Mario Brothers 2
Playable Characters:
Mario, Luigi, Princess, Wario, and Yoshi
Mario Average character
Luigi High Jumper
Princess Floater
Wario Can take more hits and is stronger
Yoshi Odd ball character...plays like Yoshi, but with more restricted controls for the SMB2 format.
The game has 3 ACTS. One with levels leading up to fighting Wart, then a set of traditional Mario levels with Bowser, and ACT 3 would be a surreal combination of Traditional Mario and SMB2 blended games with the final Boss being Wart and Bowser at the same time.
Additional powers could be: Aiming and throwing items in at least 4 directions possible 8.
Double and Triple Jumps
And I sure there could be much, much more.