Honestly, there should not be a Mario Warriors game, seriously. Stop shoving Mario everywhere Nintendo, don't agree with Tecmo if that's the series they want to do next.
Fire Emblem is the obvious choice. Not sure how Pokemon would work. I think Kid Icarus would do great too.
But I'd like them to try Metroid in a couple of years.
A sci-fi Warriors (or....Marines) game has not been done before with alien tech and shooty things and other stuff. Plus Samus and the Hunters would be great to play as! 










