Initially the 1, 2, 3 letter names could be reserved for internal use and for the 4 letters and up a donation of a certain amount of sats could be asked inversely proportional to the length of the name. For example for 1,000 sats someone could get a 10 letters name. And up with the same logic to g...

Or another way to self finance could be that a certain amount of "shorter names coupons" could be given out as reward for example for people and orgs running the federated relay system.