Populating a rouge's gallery could be taxing mentally. Tables are good, another option would be to take the PCs copy and then twist them. In most cases that's what Batman's foes are. Joker is a reflection of Batman's let's say not quite sane lifestyle. Penguin is a grossification of his upperclass heritage. Two face is a reflection of Batman's dual nature. Etc etc.
Moriarty is a twisted Sherlock Holmes, almost a mirror image of him.
So take the aspect of the PCs that stand out, copy it and then twist it and you have their arch nemesis.
How to accomplish that, well that's up to you.
I'm also thinking that this setting would work really well if the players have a lot of narrative control. Maybe if you borrowed from Open Wushu the idea that the more complicated and outlandish your descriptions, the more roll bonuses you get? I don't know if that's the direction you're thinking of but it's an idea.