Probably can use something similar to bitchat

GitHub

bitchat/relays/online_relays_gps.csv at main · permissionlesstech/bitchat

bluetooth mesh chat, IRC vibes. Contribute to permissionlesstech/bitchat development by creating an account on GitHub.

so maybe distribute the events on 5 relays depending on the region

That's not a pragmatic solution. If relays are not incentive aligned, relay providers will treat as spam what the author would have paid for, simply because the relay can't handle this user's demand. Relay operators now assume that a pubkey creates at max some dozens of events per day. If they charged according to hardware use, they wouldn't have to assume anything.