This is a topic of discussion that happened a while back in this thread, but I didn't really have a good answer for it back then, about what franchise should Fujino choose for his next big game (After finishing Sao and his Fate games in hiatus). And since we still have a full day to go before the next weekly report I thought I would start up the discussion once again.
Taking into consideration a few things, like the protagonist having to have a established relationship to get cucked in the first place, and having an appeal for Fujino's patreons, I thought about three different series could work for him.
Monogatari is something that I don't think I have ever seen in a H-game before, but it is fairly popular, the protagonist has both a girlfriend and several girls that want him, so it should have plenty of possible ntr scenarios. The problem would probably be in the characterization of the characters, it would be hard to properly portray them, but it is not like Fujino's strength is in those areas either. There is also the problem of some of the heroines being too young, but he could always ignore them or write around it. (Like Shinobu having access to her mature form for "plot" reasons)
Highschool DxD is similar, in the sense of being popular and having many heroines that are interested in the protagonist with several of them being actual members of his harem, so there would be an infinite amount of ntr possibilities. The biggest problem with the setting would be the comparatively weak romance between the protagonist and his heroines, so the ntr would be less striking than those of FSN and SAO (Even if there would be more of a connection than with Nero)
Persona 5 while not quite being anime, is probably a great setting for ntr possibilities if one where to tweak a bit with what is cannon, as almost every heroine in the game is a romance target, Fujino could chose anyone as the main ntr target, so he would have the option of having the rest be corrupted as side-stories like with Suguha and Alice.
Having yapped all that, I have to say that personally, beyond the idea that Fujino should branch out from Fate after having already three Fate games, I would prefer a new FSN game where Saber is the main corruption target, but only if the game was more like this game with a proper story to it, instead of something like Sakura's Chapter.
