I would love to see Hush in the third. I agree he fits perfectly. I don't think he is popular enough and he would need a main villian to go along with him like the penguin. Or maybe Hush is two-face's surgeon (not for his face but to save his life). Then the two become partners. I'd watch that.
Hush's wiki
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http://en.wikipedia.org/wiki/Hush_%28comics%29)