I meant the bath part, my fault, should have been more clear. All choices already in the game have the associated assets and content, adding new choices would be adding content. If I've got this right, you mean that scenes already in the game and locked at a different level of interest where she would act differently from the target level of interest should be added to the levels of interest they aren't available at. The issue with that is they wouldn't fit in the context of the situation at that level. Variations would need to be created to reflect the difference.
Sure, but if the issue is for RP reasons then the covertly / openly jerking off choices could be dynamic in the same way that the original jerk off choice is.
Currently from low interest to high she:
1. Has no idea that you're masturbating,
2. Suspects it (I think the dialogue is slightly different),
3. Knows you're doing it but doesn't stop you then calls you a pervert,
4. Turns around and blows you,
5. and with high interest and aphrodisiac she goes right to vaginal sex.
At low interest covertly jerking off would result in either 1 or 2
At low interest openly jerking off would result in her catching you and the brother needing to make an excuse (I think that happens by chance at low interest anyway.)
At high interest covertly jerking off would result in 3
At high interest openly jerking off without aphrodisiac results in 4
At high interest openly jerking off with aphrodisiac results in 5
So you still have the context based on her interest and the RP nature of either covertly or openly doing it in the choice gives further context.
it's true that 1 and 2 wouldn't fit the context with high interest.
But 3 does. She could be unaware until after he cums but then she would definitely realize what he did because of her experience.
I don't think any changes to text or visuals would be required, and I don't think any further context or explanation would be required for it to make sense.