I've explored using LLMs for this exact purpose, and there's a huge problem. Onlyfans rules very strictly forbid incest and other kinds of icky content, and Onlyfans sexters are very, very aware of this. If you break the rules, Onlyfans is very eager with permabans, and getting your account banned effectively destroys your whole business.

When it's that easy to screw up, it's easier and cheaper to pay real humans $1k a month for sexting than to build an LLM-based system that never makes mistakes and is 100% secured against prompt injection.