Burning funds, instead of transferring them, would solve two of your three issues. Obtaining the funds creates extra friction, yes, but it’s possible the benef

Burning funds, instead of transferring them, would solve two of your three issues. Obtaining the funds creates extra friction, yes, but it’s possible the benefit outweighs the cost — e.g. because an attacker can no longer utilize the idle CPUs of botnet devices. Ultimately, any form of anti-DoS protection also punishes legitimate users. The question is (1) how much it punishes attackers relative to this, and (2) whether this punishment for legitimate users deters them, too.