Hi Leafo,
Instead of trying to find a new payment partner, what do you think about playtesting the adult games on itch before they get published, and then just use Stripe to let users pay for them? Like that, you're sure that the paying adult games are following Stripe's rules. I know playtesting all adult games would take a lot of time, but you could charge something for that, either by a one-time fee at publication time or by a minimum revenue percentage that Itch keeps. I know I'd be willing to pay a "playtesting fee" to be able to sell my game on Itch, if that is what it takes...
Kind regards,
ilPazzo