Which is scarier, that a creature is literally eating you from the inside out or that it might ruin your chances at getting laid? Never mind we all know the answer.
Technically speaking this would make it easier to filter and cleanse the (concentrated) bad air inside the dome. It’s not feasible for a bunch of other reasons, but this one we at least have the technology to handle right now. Maybe not at the volume needed but that’s a different issue too.
The difference is the medical definitions of cause and factor. Lack of breathing will cause death. Obesity from eating too much sugar is a factor. If it was a cause eating too much sugar would CAUSE it to happen every time. It does not.
I’m not against a “gangster” version of the Joker, because a lot of the Batman lore is about the different gangs of henchmen so the Joker is as much a gang leader as anyone else. AND I’ll go out and say he was not the worst thing in that movie… but yeah they could have done a lot better with the casting. But hey, still better than Eisen-Luthor!