I'm not saying he shouldn't make the game he wants to make. He definitely should, but yes, it's a gamble, and yes, he will lose supporters.
Fans of Femdom, and NTR, don't usually play only those adult games, they just tend to favor them. While Femdom, and NTR haters will not play games that have those fetishes.
Another example. Incest, and Anal, are my top fetishes, I definitely favor games that have a lot of that content, but I still play other adult games, as long as they don't have fetishes I hate, like Femdom, and NTR.
Catering to the divisive fetishes will get you some rabid fans but eliminate others. That doesn't mean those games cannot be successful, but it limits the scope of the success.
Still, at the end of the day, there are far too many adult games, and not enough dollars, for them all to be successful, so any AVN is a gamble.
The best way to hedge your bets is with a good story, and regular updates. If you have that, you have a decent chance of pulling it off. And the Dev should always make the game they want to make, or they will end up hating it, and burn out.