since if we had a batcave on Arkham Island, it'd be safe to assume/hope we'll have one in this game:
how about two different batsuits that you have to go to the batcave to change from one to the other, each very different -
A Stealth Suit, low on gadgets, very light and fast to move in, glides further, very quiet when moving about in, low armour, easy to perform large combo's in, easy to disappear when seen.
A Muscle Suit, high on gadgets, heavy and slow to move in, doesnt glide as far, muscle suit therefore hits harder, high armour, difficult to perform bigger combo's.
Making the two as different as possible, but so the player doesnt have to keep going the batcave to change, make sure each one can be used to complete a task ie every situation can be dealt with through speed or muscle, stealth or gadgets... and to do so you have to play very differently for each suit
EDIT:
this link may help with clues to possible villains -
http://www.bigshinyrobot.com/reviews/archives/11061