To incentivize people to run publicly facing relayers, and discourage people from DDoS-ing them, it would be neat to be able to have them charge a "toll" for requests and filter out bad requests at the network/firewall level. This could be accomplished by having some kind of "register a wallet" endpoint, allowing wallets to then subsequently include a signature/hash in relayer requests similar to how HMAC works in the packet headers. This way, requests that are not signed by allowed/registered keypairs can be blocked more effectively at the firewall layer, instead of overloading the rpc node.
