Actually, i saw this in this game. (at market you can click on Deny tits, and they will bounce a little bit). So, I`m not sure about Oni`s skill in that area, but it`s totally possibly to do. Just add variables like "if love=< 300" don`t accept touch(=face slap), "if love=>300" accept touch(=get undress) and trigger text balloon and animation.I don't even know if Renpy is that much in depth for that then again I've never seen Renpy at it's full potential anyways
The same mechanics goes for undress. Touch button on her blouse/skirt/top and so on, and get a result - face slap or undressing.
For me, this game is great, but i wanna have some "direct" interaction with girls. And also, i think menu is a little bit overloaded with actions.