Not having a safe word is maybe over the line but I feel like in general that’s just a case of indulging in a partner’s fetishes/fantasies. It isn’t really rape if both of you consented before hand, it’s just role play. That said, I’d probably also want to meet somewhere in the middle, I’d have a hard time continuing if I was being asked to stop, even if consent had previously been given.

Pretty sure somewhere on the internet I read that this was a super common fantasy, but I don’t want to do the research to confirm. There’s probably nuance to it, but it’s definitely uncomfortable to consider.