Bring World Pass to FFXIV!
Make an invite code that allows new players to create or transfer over to join you on the World that you are on. FFXI had something called World Pass that did this.
Some players want to create on a locked server to play with friends but can't try during early morning because of work schedules. Some players don't have any real reason to choose that server but they picked it randomly because it was available. An invite-only server reduces this problem.
First, servers can be set to Open/Auto, Invite Only, or Locked. Low population servers are kept on Open/Auto: the current behavior where character creation is freely allowed until logins reach a certain rate. Passes can be purchased to bypass the automatic restriction. Invite Only means that a Pass is always required to create on or transfer to that server and it will not unlock during early morning hours or right after maintenance. When a server is fully locked, no more passes can be purchased, but existing passes will be honored.
The pass would be purchased with a large amount of Grand Company seals, let's say 10000 seals (price of Keeper's Hymn), or an insane amount of gil e.g. 4 million gil. When you purchase it, a code is sent to the purchaser by moogle mail or email. You tell your friend the code, they enter it in Mog Station and the very next character they create or transfer will have your world unlocked. To reduce hoarding and selling of codes the code must be used within 7 days of purchase. The price can be automatically adjusted by the server based on login rate or manually set.
Invite-only means less people creating on Balmung just because they heard it was "the RP server". If you want to invite a friend to Balmung, that will require 20,000 Grand Company seals. If your friend wants to play on Gilgamesh but they are working during the time that it is open, that's not a problem. Craft some stuff, sell it on market board, pay a few million gil and text message your friend the code. Now they can get on anytime.