To grab the boob without consent is sexual assault. An accidental bump or cup does not come under this because it concerns intended grabbing of boob.
To suggest a 'structure' for progressing seems rather restricted, one fun game is to see how far you can get without kissing, another is how far without using hands at all, structure for how people do their relationship under a law? No thanks! Teach people how to be decent human beings? Yes please!
Also, to know when there is a green boob grab flag requires the ability to read body language, it's not too hard once you know what to spot. So in a way, they're observational powers, which are often mistaken for psychic powers.