You have full control over the nostr.json file in Settings, and can use it to create usernames like [email protected] or [email protected]
We don't have a fancy UI to add users yet, so you will have to consult the NIP and type the json by hand: https://github.com/nostr-protocol/nips/blob/master/05.md#example
You could sell those usernames, or issue them to your biggest fans, or come up with your own crazy idea!
If you need help handling this, let me know!