Title says it all, is there any mod that gives you more options in sex interactions with when you have 4-5 participants (player included)? 3somes work quite well and have variety, but once you add the 3rd slave, your choices are drastically reduced in the vanilla game. So, are there any mods or mod that address that? Give more options and the like?

I'm not aware of any orgy mods. It wouldn't be hard to make one, but it would be kinda tedious.

The mods that most significantly changes sex are the Expanded Sex and Chastity Belt mods, including a few new sex actions. Aric's and Ralphs mod slightly alter sex mechanics, but not in any way relevant to this.