Unfortunately there is none of that at the moment - for example, there's an Animal Breeding / Farming mod out there, but the current mechanic they use is just pair two of the same NPC and then feed them both. There's no designation for one being male and one being female.
Yet.
I have an idea of how it may happen, but it may just break everything. So I might have to wait until greater minds get to it.
I've just done the work to make an appealing set of base, detailed genitals to start, and work as source materials for those whom may introduce the "mechanics" that you speak of, haha.
I'll work on horses soon also. I already also have a horse vulva, but I've noticed someone has already made a pretty decent horse cock - so that work might already be done.
Will see.
The one thing that Skyrim had going for it, was there was complimentary, two character trapping animations already. There is no mechanic like that for Hytale yet, that one animation might lock a second NPC into a responding counter-animation. Grappling, dragging, etc. So it might come down to turning NPCs into statutes/furniture, or invisible, and then spawning a copy of the two NPCs performing coitus as a statue performing the animations.
The latter might be the easier to perform and give freedom to move around the "fuck statue" performing the animations.