Just watched 'Assault on Arkham', I'm convinced this potentially could be quite brilliant. Interesting premise of breaking into Arkham and causing absolute mayhem while introducing a load of characters to setup future Bat films could work quite well. Hell, they could even loosely bring in the Nolan Batverse, why Joker is in Arkham and how in comes into contact with the Suicide Squad. Those lesser villains are definitely dying though
Solely going by Assault on Arkham, one potential annoyance, there would be a hell of a lot of Will Smith on screen time