Hi Pukka,
As I don't want to 'throw off' the game's balance, the heroes stats are simply those taken from some of the numerous official Survivors. All we do is rename them and rebrand their abilities to tie-in with the super-heroes.
We simply use our favourite A-List super-villains as Fatties for now, so it really is a case of just grabbing the usually larger models and plonking them on the table. My bigger "Heroclix" re-paints, such as Tess-One, are set aside for Abominations etc. We don't use any non-generic figures for walkers/runners, to try and keep is simple and make them instantly recognisable on the tabletop.
None of the rioter have range, even the ones carrying handguns, they're all just normal walkers/runners. We also run a campaign with "Blake's Seven" verses "Aliens" and in that one we simply treat the aliens as toxic walkers/runners and Fatties. The BatReps are on my blog if you're interested in seeing the mechanics in action.