We kinda went over this countless times in different threads and I'm sure SE went over this aswell before they decided that the best solution was to lock Balmung.
But here it goes, let me adress all the points seperatly:
1) Merging - Means they'll run into a lot of problems. Starting with housing (who keeps that Shirogane Ward 1, Plot 30 house? The FC from Balmung or the person from whatever low-popo server you're preying on?) all the way to characters with the same name (again: who has to change?)
2) Incentives - its honestly sad to me that you're bringin this up... considering that your initial reason for unlocking Balmung was "I want to play with my friends" - if being able to do that isnt motivation enough for you to switch server, I dont know what will be... specially considering that we're having several servers with RP-communities now, dont we? Mateus as alternative for NA, Omega for EU. Maybe not your "Balmung-atmosphere", I dont know, never played on any of those servers - but if thats worth more to you than friends you've made your choice.
3) Crossworld-Features - They've already said they're working on that. It just takes time.
And frankly: Locking the server to get it down to healthy (for the hardware) numbers worked once. This time they probably locked it to keep it at those healthy numbers.
Saying you cant leave is bullshit - you can leave at anytime, even free of charge. You just dont want to - thats okay if thats your choice, obviously.
But keep in mind that an overpopulated Balmung is more harmful because of server-stability for the wholer data-center than a locked one.
