I've not seen many hero suggestion pages so I'll go ahead and say it:
I want Crystal.
I mean, she has control over the elements and since Black Bolt has introduced the Inhumans, it's not impossible.
She could be a class changer, with each class being a different element. For example:
Fire = Blaster, Water = Tactician, Earth = Bruiser & Air = Infiltrator.
Please comment on any thoughts you have!