The SFW GAME CAMPAIGN was supposed to be that, and that always came AFTER the porn game, that's a looooooong way out.
Well, that's not how you make a product that is supposed to keep your customers loyal and satisfied. The easiest way to achieve both – rewarding gameplay loop. Anthem didn't have one – it died. NMS has one and it expands on it – it succeeds.
Harem mode is not that loop. Promised Erotes club (it is probably going to be what the original fallen doll was) also doesn't have what it needs. But the XCOM be it SFW or NSFW. That's exactly where this loop could and should have been! Similar to Azure Lane or FEH where you get rewarded with things that improve the what is now "gacha" part. Consumables, currency, some items that can be placed around the scenes, etc.
Or even better! Make it a goddamn Pockemonlike game where xenos have their own skills/traits/lvls/grades and can be caught/improved and used later for some multiplayer challenges/duels or whatever.
I'm sorry for this long essay but as I was saying porn parton its own wont be able to keep people
paying playing this game. The rewarding gameplay would. Porn part is just nice addition and (as it is now) a gacha.