FicWad

definitely going to be a good story if you continue with the writing as you have been going so far.

riddler- fits hermione almost too well

scarecrow - couldn't fit the twins any better, what with all there creations making the fear stuff wouldnt be too far fetched.

two-face - ron since he seems to have two different personalities for most of the cannon story wouldnt be that hard for him to go over the edge

bane - neville accidentally stumbles across the venom when working with a plant in his green house at home has mind and body altering affects with the first use

black mask - charlie once he heads off to be a dragon handler, ends up mixed in and takes over an large crime syndicate

catwoman - cho chang cant really explain this one but who wouldn't want to see her in catwomans outfit

clayface - tonks exposed to something that has a wierd reaction to an ability or percy due to some wired experiment of the twins. either could fit real nice as clayface

Harley Quinn - ginny not many others that could be this dedicated to harry, especially with him being the joker, could have her be twisted by the horcrux before she tosses it.

Mr freeze - luna side affect of a spell creation of her mothers

penguin - cedric digory looses his looks in a childhood accident and is permanently disfigured after which befriends the birds in his families aerie

poison ivy - fleur powers seem kind of similar to a veelas



if you are going to include some of the rare appearing badguys

Ventriloquist & Scarface - luna the only one i could see convincingly pull this off with mabey a snorkak dressed up as scraface
Hideto Katsu - blaise zabini
Kabuki Twins - padma and parvati
killer croc - oliver wood but could be just about anyone stuck in some messed up partial animagus transformation
man-bat - marcus flint another messed up partial animagus transformation
ragdoll - could be tonks if she isnt clayface

Jokers henchmen
Marty, Punch and Judy the Griffindor chasers

riddlers henchmen

Riddlemen, houseelves with peronsailty modifying hats


several other bad guys that i just couldnt find anyone for, that you might want to look up if your having a hard time tring to figure out who all you want to use is
http://en.wikipedia.org/wiki/List_of_villains_in_The_Batman