What will their bio be if these are possible monster girls? Imo this is what I think:
1. Female Ancient - Researcher studying lifeforms on earth & maybe their possible connection to the lab accident
2. Female Demon - She'll already be an established queen who drops greater & lesser demons but lost her mate so she's in search of a replacement to reproduce
3. Female Centaur - Emigrant from her village to Weirdtown looking for a place to stay & found a home in Beth's stable
4. Female Satyr - Virgin arriving in the mc's family farm & decides to pull her weight by producing milk
These are so far the only suggestions I can come up with
1) I dont think the Ancients are aliens. From the sounds of it they are the original race of the World & in their genetic experiments to gain immortality they ended creating all the races (humans, elves, halflings, dwarves, giants, goblins, orcs, ogres ect...). This would explain why all these races can crossbreed. They all share the same genetic origins. The only way I see them working is either some managed to ascend to god-hood or they became the Fae (Tinkerer mentioned far are an "inbetween" species that exist between the 2 planes).
2) Interesting but we already have a Succubus & an Imp. I'd rather an Angel tbh.
3) I have nothing against this...
4) I feel like the Cow Girl is going to be milk heavy in her theme (& Rosy had a milking thing as well) so I kinda dont see a Satyr being apart of that. I feel it just become a boring re-hash of the same theme after a while.