Thanks so much for making this mod! I wanted the relationship/romance/sexuality system expanded upon and here this is!!!
I see you would one day like to add poly, great! You also put in asexuality, good! Other than just asexuality, it could still be pretty neat to have a low sex drive trait, as well as a high sex drive trait. Putting in swinger or 'in a open relationship' as a trait might also be easier to implement than a poly marriage/dating system. If they have that trait then there's no debuffs if they 'cheat' on their spouse. Perhaps with an increased chance of them to have an "affair".
Oh, if males are not bisexual in-game please add that in. I know women can be bisexual in-game, but I know it was only females who could be in earlier alphas.
If you really wanted to go in-depth with this you could try to implement a Kinsey scale system of some sort. You could have a male or female that's traditionally identifies as straight, but experimenting or is 'just curious' and has a one off affair with samesex colonist.
Oh, having casual sex vs romantic dating is a nice touch. It'd be fun to see the drama when two folks get together, one not ready to commit and wants to just sleep around. Imagine that debuff when a colonist gets broken up with/broke things off/let's just be friends.
Please add an incest trait that has the bearer ignore family flags and they try to romance their own family members. I'd also suggest adding incest gossip to your other mod.
Perhaps you could consider adding bestiality to the game. I just think it'd be funny as hell to see one of colonists be all hearts by a muffalo or something. The colonist gets lovin' buff still, but everyone's opinion of him decreases if anyone sees.
"Steve? Steve! What are doing to that Alpaca---oh gods. Why?! Why?!"
If implementing such a thing would be a pain, then perhaps at least consider putting it into your rumor mod? It would make perfect gossip material. "You know, Trake's always spending all his time taming muffalos or milking them. It's just not natural." Or "I heard funny noises last night coming from Trake's room."
One last thing, I know vanilla games have masochist and sadistic traits. If they're not configured to do anything further, could you put in the ability for a sadist colonist and a masochist colonist to do 'activities' together? Not sex, but you could just use the heart sex animation for the two and say X is flogging Y in the dialouge box. Or whipping, whatever. The kink/bdsm shout out is already pretty much there in the vanilla game. D: Other than sadistic, folks who are into bloodlust or violent, brawler etc should be approached by masochist colonists. Each with different levels of success rate [bloodlust = 100%, brawler = 40% or something].
(Real last thing) Consider putting into your mod settings the likelyhood of sexual deviancy, so to speak? In other words, the ability for someone to crank the lgbt (+kink/bdsm) chance of from 5% to 15% etc. Oh, and if you do my suggestions of incest or bestiality traits then I guess an option to turn those off as I'm sure someone would rather not have it in their game.
Sorry for all of this, I'm just really interested in these systems. Adding these sorts of things in makes for more interesting and crazier stories to be told. Which is fun.