Honestly, there's probably enough demand to base the whole game around it if you wanted to. I'd wager 90% of the people who clicked on this game clicked for the beast tag. Or saw it in combo with the real porn tag and WTF clicked.
Yeah. I get wanting to have a wider audience, and there are a lot of people who get upset about bestiality (and a smaller number who get upset about incest), but trying to please everyone is going to leave you,
NaughtyNeighborGames, with a bunch of frustrated players who came because they were expecting one thing (a game with "Farm" in the title that is primarily about bestiality, incest, or both) and ended up with a few scenes for each and most of the content about fairly vanilla stuff they can get anywhere. Also, keep in mind that the more you split up the game with big decisions like that, the more time and effort it's going to take to develop everything: each scene you write, you're going to have to consider if it shows up in the vanilla path, the bestiality path, or the incest path, what changes need to be made to keep it consistent with those paths, and also how each version is going to be affected by other choices along the way.
Also, honestly, if you want to make a bestiality game, then make a bestiality game. Worrying about what other people want is the best way to strangle your interest in writing a story.