I like that idea a lot. Don't know how feasible it is with animated sprites, but it'd be great.
There's also the issue that a lot of the dark clothing layers would obscure this, so it might need to be exaggerated to an unrealistic point in order to be noticeable with dark clothing. Plus also clothing layers, so normal bras might obscure this (which is realistic, but ineffective for game purposes), while sexy bras, corsets (can't remember if this is in game yet) and no bras should show. But game drips even with panties, so maybe verisimilitude instead of realism...
Finally, if a girl was really that steamed up down there, I would advise her to get checked for a yeast infection!!