They should do a threshold system and charge extra for adult content. Adult content is bound to make a hassle, because people use report button needlessly.
The free revenue share is a silly concept. Make it only apply for yearly sales of less than threshold, like 100 bucks or so. So the unsuccessfully devs can be happy about getting most of their earned sales. While the successfull games should give minimum amount and a mandatory bonus for 18+ stuff, because increased maintanence that 18+ stuff requires.