This is a slippery-slope and it's already played out in other contexts e.g. black-sploitation.
Even "bad guys" can be good characters [0], the most complex/nuanced characters are also complex. Start dictating that <x> characters can't have negative attributes, and you end up with boring, simplistic caricatures of <x> thrown in as tokens, but never managing the highlight (because why would you want boring, restricted characters to be in central roles?).
[0]: Is Gregory House a good character? Is "Dexter"? What about characters from the shield, or breaking bad?
Even "bad guys" can be good characters [0], the most complex/nuanced characters are also complex. Start dictating that <x> characters can't have negative attributes, and you end up with boring, simplistic caricatures of <x> thrown in as tokens, but never managing the highlight (because why would you want boring, restricted characters to be in central roles?).
[0]: Is Gregory House a good character? Is "Dexter"? What about characters from the shield, or breaking bad?