It might help, but it just wouldn't work. Like Cucumba said, people would get powerful quickly using Vegeta's strong attacks, then switch to Goku and be able to go SSJ 3 (assuming that will be in one of the later releases.) Anyone who really did want to play with just one char would lose out completely.
I mean, imagine someone with a 40 million pl as vegeta suddenly changing to someone like Trunks with his super fast Burning attack. It wouldn't matter that the attack was weak, he would be so strong that it would blow everyone away.