There's few problems with that.
1. People want character in smash to play him in smash. That's reason why people want some character in smash, and/or character being represented. That's an ok feeling and for which everyone would want someone in smash.
2. Phoenix in MVC is not why people want him to see in smash, it's why people are believe that Lawyer can be playable in fighting games plus G&W, Wii Fit Trainer, Duck Hunt Dog, Captain Falcon, Animal Crossing characters and many others exists in smash and fit well, it's not necessary for a character to be able to fight to be in smash.
3. Phoenix have different moveset in Smash Bros crusade, there are 2 videos on YouTube where people abstracting from MVC giving him another moveset, and using MVC only sometimes for reference.
4. Like his MVC moveset us bad? His moveset on it, is one of the very unique movesets for a fighting games which fitted well in MvC.