I'm not interested in sex scenes that do not involve the MC that counts for lesbian scenes and for Futa/Female, additionally, if you offer too much optional content updates will feel small for players that don't like the optional stuff and they will think you are wasting development time on content that they don't see.
All the game will be in first person perspective, so third person scenes (with sex or not) would be minimal. In other words, practically all sex scenes would involve MC as an active participant, and few of them would have it as only an observer or not present (i.e. the Futa/Female scene planned so far is a trio with Deb and one of the girls).
About the optional content, to make it sort: The main content would be focused in netori and corruption with the main girls and will be plenty of it, all the other things will be extra scenes that you can avoid if they aren't your cup of tea, and will be added in more or less quantity depending in public opinion (right now I think I will have to add some more Deb content, as it looks like she is making people excited over here...).
For the dislike of Unity, RenPy has some features mainly the easy saving and rollback that almost all Unity games are missing. Also, I like to use Walkthrough- and gallery-mods and they are much more common for RenPy games and the few gallery mods for Unity games I've seen are terrible. So in the end RenPy games are more user-friendly.
I agree with you and sadly I won't be adding a rollback function for the moment (never say never), but to compensate for that the game autosaves everytime you get a choice so you can load back if you want to make another, and even if the UI is not implemented yet the game tracks seen text even between loads so you can skip it. I will also add a dialog log window in the future so you can review past text.
For the other things, easy saving is already in the game in Ren'Py fashion (right click to open menu, save/load anytime you want), a gallery menu is already in the roadmap and a hint/walktrough system will be developed but there isn't an ETA yet for it (the reason being that I will have to revamp the UI in the future and would be better to implement it when that happens). I aim to make my framework as user friendly as I can and with all the functionality and mechanics that a veteran VN player would expect without the need of second-party mods (even tho, I would love to create a modding API as I stated in the roadmap, but to be honest it is low priority right now).
I hope to have addressed your concerns!