Indeed. The thing you need to be careful about, is to try to not dilute the class pool too much. It's a tad hard to make every class unique when you end up having 15+ classes to choose from.

At any rate, I seem to recall Yoshi-P saying that they want to fix the most egregious problems with the game first, and balance all the current classes. Only then will they attempt to add more classes to the game.