Hey, I'm also interested in that, since the idea of an optional "hard mode" like that is so underdone in games (I think only Love, Sex, And Second Base does it?) Though currently the dick upgrade is part of the Kill Pig Curse, so working that out would be a bit hard.
Also, damn, I can tell why people asked for that, because the public nudity scene, nickname, and the Stepmom's attitude really fit something like what labbu wanted. I don't think you were intending that, but it really felt like an unintended signal fire.
The most painless ways I can see to add that would be just making a route/routes where the Game Master says "Oh, by the way, [insert girl here] doesn't like big dicks, so I'm returning you to Thumbelito mode". The downside of that is some people might not like the character that gets that treatment, and it also is going to have people saying "Hey, I don't want to do that", so they'd probably have to be optional? The other option would be just making it a optional thing for you to not have your upgraded dick for some of the characters going forward.
Anyway, about the game itself. I know it's early, but that wall with the "you need karma to progress, get the master hints!", and all they do is give you the karma needed to continue the scene felt so damn silly. The situation itself felt kinda silly too since Option 2 is literally just 2 combined with option 3, but I think that was supposed to be a joke? It feels like if the hints said something, something about game master making fun of him for thinking Option 3 was the correct choice would be funny.
I think the "normal" speed of the second sex animation needs some adjustment, it looks like it was several frames too slow IMO.
Are you also doing all of the art? It's quite nice, you'll be able to cover a lot of ground with what I've seen of it so far.
So, yeah, overall a pretty decent first second game, keep it up!