some questions on the limitations on the powers, in-order to get to know your theme/general power limits.
Would you allow masterminds who's specialty is based around making advanced or unusual devices or machines? either sci-fi or magical in theme.
the ability to create/command minions like goblins, invertebrates, squirrel, metal/stone shaped into rhinos etc?
Are the powers requiter the individual to be able to pass as default human with no physical alterations to the body?
If you allow Animal Shapeshifting would you allow Shapeshifting into other things, for example werewolves or other mystical creatures, machines, some kind of themed group of monsters like Tyranids or zerg etc?
finally force-fields and shaping them into wings, weapons creatures etc?
I think that covers all the things that may or may not be out of bounds.