Not a fan of the MP idea as it's just going to be shoehorned in and take resources away from the main game.
However I am wondering if this very specific list points to some of the characters that may be trying for the bounty on the Bat's head?
some kind of Electroman character
Electrocutioner maybe? What do you think Aoife?
I'm with you on that Cunning, no to multiplayer... at the most a fully optional co-op campaign separate from the main campaign and without micro-fecking-transactions!! Don't get me wrong, if they offer something wholly innovative that doesn't leech the resources requiered for a decent main campaign then I'd be all for it, but I doubt that'd be the case.
I can think of a few ways they could innovate, a game I'll coin as "Anti Co-op", where two players go head to head in story based missions, for example Batman vs Riddler, where player one has to solve challenges / traps setup by player two. Admittedly I haven't hammered out the details of how this could work, that's not my job!
Secondly 4 player Versus. Batman / Robin (or Catwoman for that matter) vs Joker / Penguin (or Harley Quinn for sexual equalities sake) in open world shenanigans.... but like Ed says, I can't see how the existing combat system could be shoe-horned in to multiplayer effectively.
Best they leave alone I reckon, multiplayer is not needed. I'm only just finishing the GotY version of Arkham City which I picked up brand new for the bargain price of £14.99 recently! I performed the same cheapskate tomfoolery with Asylum... and with the threat of a probable mediocre multiplayer eating a chunk of the development budget I'm likely to wait till a price drop and innevitable GotY version with all the DLC comes out.