(Edit - I just read a post that they already have the theme idea, read this knowing I hadn't read that yet)
Well, you have a chart that gives the combat roles, Bastion here, Ranger or whatnot there. The chart makes a 2-D square. All righty. How about making it a cube by adding in themes and/or elements.
Martial Arts and Weapons
Energy Blasts and Auras
Magic Armor and Weapon
You could make this related to the Focus mechanics, and also allow one or two power themes, allowing them to be stronger or more diverse/adaptable. It would make sense that only certain themes would work well with others: Demon Form goes with Darkness Powers, but Plant Form doesn't really have a synergy with Gizmos. Not that there wouldn't be a rare person who could make that work. Just that that would be horribly outweighed by the number of people making goofy characters.
I saw a werewolf with a Chinese menu in his hand,
Walkin down the streets of Soho in the rain.