it pretty much already is, and it’s really not worth enforcing… to what end? it will make negotiations less frustrating maybe, but what benefit is it to the mods? and, i don’t see it weeding out too many scammers. again, i know plenty of primo folks that bst this way - but i can view it from some buyer’s perception as well… besides, if i see that in an ad, i consider that additional room for negotiation anyway 
adding more rules… requiring g&s, how would that even be enforced, and by whom? we have veterans that aren’t following the existing rules… @codinghorror had a great point the other day, their are puh-lenty of other bsts, but i think he was thinking about it incorrectly. sure there are others, but this is one of the highest quality. if you’re going to put rules in place, make rules that will contribute to the overall quality of the bst. even the point leveling system, 2, 3, 4… it’s essentially meaningless… give me a weekend and a stack a bananas, i’ll train a monkey to give enough likes to be on the bst…