Ivy and Freeze could both work I think...if you can buy that there's a leauge of ninjas who've been secretly conrolling world affairs for thousands of years, I think that it woudl be acceptable to have "super powers" like those 2 have...Freeze doesnt even really have powers, he's just a guy with a weird medical condition caused by experimental chemicals...and you could always ditch ivy's plant control powers (which never made sense to me anyway) and just give her the toxic kisses
the more I think about Croc, the more I think he could be done too...make him into a sideshow freak/strongman type guy...