It seems like a protocol change to enforce a minimum transaction value would make sense. There is a 'dust' limit, but I believe that's just relay policy; and by default, it's only like 546 sats or something like that. If UTXO's were instead forced by consensus rules to represent a more reasonably useful value (in sats), it seems like that would a) add more disincentive for spammers to create a bunch of otherwise useless UTXOs; and b) the otherwise useless UTXOs that do get created would make useful sats that much more scarce... all without having to judge what is spam and what isn't. I assume I'm missing something, though, because this seems like such an obvious mitigation to me; but that I never see discussed.