Oh, okay, give me a moment. I can tell you exactly what you'd need to change if you can decompile and get access to the source code.
If you CAN decompile and recompile the code, go into ./Assets/Scripts/GlobalNumericVariables.cs and you can alter lines 607 (to change the lingerie costume) and 612 (to change the all-in-one costume) to better fit your liking. If it doesn't decompile exactly like that, you're looking to change the constructor's initialization of the variables
INTERACTION_DURATION_INCREASE_COSTUME_EFFECT and NAKED_INTERACTION_INCREASE_COSTUME_EFFECT
I think, if I were designing the game from scratch, knowing what I know now I would have set up a read from JSON and made it publicly available to do a lot of thse, but as it is now, it's too engrained for me to do that.
Alternatively, Tobe did post the source code in this thread somewhere, so anyone can download it and Unity 2019 and play, and I would not care if anyone else did the same and made their own branch, so to speak. In fact, a sufficiently interesting branch, I'd likely download and play myself!
Wasn't my baby back then. And anyone whose wanted to mod and change and alter to their liking has my blessing.
Hey, that's how Happy Hour started. There is, absolutely the ability to do so. And I don't mind.
EDIT: I uploaded my working copy of the original vanilla
source code here so all you'd need to do is download a copy of Unity 2019, go to what's listed above to find the line, rebuild using U2019 (NOT 2021, save yourself the gray hair) and bob's your uncle.
EDIT2:
Happy Hour source code.