Let's see, here's all the possible team-ups:
Mario & Luigi
Mario & Wario
Mario & Waluigi
Luigi & Wario
Luigi & Waluigi
Wario & Waluigi
That's six. If you take the three original special move types from SS: Jump, Hammer and Hand and apply them to the above six teams (one for each Bro on each team), you get a total of 36 possible move opportunities. It would take a really BIG game to apply all of them, and naturally all four Bros. would have to earn them at the same time when you receive the Jump and Hammer.
This isn't even counting whatever M&L and W&W exclusive stuff they could add in either. There's enormous potential here, folks.