I understand what you're saying, but that's kind of putting the cart before the horse. If the NFL didn't care about marijuana (and IMO, obviously, it shouldn't), it wouldn't test players for it. So there would be no suspension for that and no "terribly stupid thing" like getting caught on an announced test for it.
As for arrests, I can't imagine anyone doing time for smoking the stuff, although I never was caught back in the day. Seems to me that possession of a personal use quantity charges seldom result in jail time (so the player won't miss practice or games) even in the rare instances in which they're brought.