I'm not talking about selling as in paying cash for it. Someone virtually cosplaying can say they are green arrow or the flash or the Hulk all they want, they aren't the real thing.
There is a very simple solution to this issue as I see it. The devs can add every variation of every copyrighted or trademarked character name into the restricted list and program restrictions costume restrictions for every variant of every comic hero including powers combo. When people start creating about the lack of customization, the GMs can forward those comments to the costume police and have them explain how someone making a cosplay toon is hurting them.
People are making cosplays all over the place. I see them in CO, Neverwinter, STO, WoW, you name it. No one is losing any sleep over them there. This is more about someone feeling they need to dictate to others what they should and should do as far as I'm concerned. I see way more offensively named and themed characters in here than I do cosplays. Nobody seems to object to those at all even though they could just as easily lead to a lawsuit.