Rather than forcing bittorrent users off the network entirely, it would be better if the access point itself limited the number of connections per MAC address to something reasonable. This would prevent the symptom from occurring.
Exactly. The problem here is the owners have not configured their access points as well as they might to serve the broader public good. In an ideal world, each of the restaurants, cafes, airports, bus terminals, subway station, etc., owners would be fully technologically savvy, and be able to prevent the ill that the OP feels has befallen the public.
That mythological world is not the one we have, where the owners of such establishments just buy an off-the-shelf solution and plug it in. They are business owners, not IT specialists, and many (most?) are not big enough to support someone like that on salary. Nor should they. The corner mom-and-pop coffee shop should be concentrating on making a good cup of joe.
If the OP really needs such connectivity, he should buy it. Lots of companies would gladly take his funds, and these days, globally available wireless internet in most cities in the developed world just isn't that expensive. Especially if your lifestyle, or income, depends on it.