I think it would be worthwhile to PR existing relay implementations. But if that fails, a custom relay implementation expressly for this purpose would be a great idea
That said, this could indeed be done with a custom relay. One that pulls in 10002 events from all known relays and allows for a query of just the first several characters of a pubkey. There is no need expect all relays to have this behavior. From there the client will have the relays it can expect to find the event, and relays DO currently support partial event ID queries, right nostr:npub1arkn0xxxll4llgy9qxkrncn3vc4l69s0dz8ef3zadykcwe7ax3dqrrh43w?
Discussion
I didn't mean custom implementation for this purpose, I think you can probably do better with a custom relay implementation.
I mean, if it's already custom you can assign a serial number to each event and map those numbers to real events in a custom database. Then convert those numbers into single or double-word mnemonics for users.
Or is that boring, doesn't contain cryptographic tricks, centralized? Maybe it is, but I think boring is good and centralized is fine as long as it plugs into the rest of the Nostr ecosystem.
Nothing else I know of can do this at a protocol level. It's like a compression cheat code. I think we should take advantage of it