Some feedback:
1 - The progress on the weaker version of Isha's mark seems way too slow, unless it's designed with the three planned mansion levels in mind. I didn't play with the faster version enabled but that one might be too slow as well. By the time the mark collects enough points to trigger the first progression scene you should have enough xp to make Isha fights feel really easy. I admit I fought Isha after defeating Bonny and Jenny so I was already pretty strong at the point I challenged her for the fist time, but further interactions with Isha still feel awkward in my opinion. I think she needs to be someohow stronger to scratch that FORCED feminization itch but I wouldn't insist on making her too "in your face" because I'm aware many players don't want that stuff in their game. I like that interacting with Isha is completely optional, I just think there should be more "force" in play once you flip the switch to enable that kind of content.
2 - Sidney seems to be important in the main story but the way she's presented in the game make any interaction with her seem obviously negative. I'm guessing you want to make her an important character regardless of our choices but I see no reason to cooperate with her in non-bad-end playthroughs. She's totally fine if she's supposed to be just one of the many mid-tier side characters in your plan though.
3 - Imbalance between red and blue options during the foreplay stance. This might be intended considering the situation is reversed in the next, direct sex stance where there are more red than blue options, but it still feels bad when you're fighting against a succubus who prefers aggressive actions and you're out of spank/grope ass/tits actions. Both "lick" attacks are tagged as blue actions, which seems to be the same kind of action as the two caress choices. I think it's worth to consider adding some kind of agressive lick, suck or kiss action.
4 - The game calls Lana "object object" at least twice. The first time happens when we run into Lana and Lucy for the first time and the second is when we ask Isha about them.