IP filters will eventually block new people as well, those using popular VPN's, ISP level IP4 gateways, Tor exit relays, college campuses, the list goes on... attackers can unfortunately get their hands on IPs just as easily as they can generate new keys
Soft forms of WoT via invite links or PoW seem more promising
WoT on relays is way worse. IP blocks would be temporary for the duration of the attack
Yea thats fine for short-term rate-limiting defense against DoS, but doing anything reputational with IP's beyond that will hurt new users even worse in the long run
Tiering works well in many environments, for example you can still allow new users with no friction but also impose a basic rate limit (or kind restrictions), with upgrades to those permissions achievable either via a PoW flow, WoT-invite flow, or just good behavior heuristics over time
