As a workaround for the world merge lockout problem, I suggest that SE lets people who wants to move to the locked worlds get a free character move to the worlds in question.

Characters created during the lockout period could get one free move instantly after the merging is complete, as long as they did it within one month of the merger, and as long as it was a move to one of the worlds that were recently merged.

What do you think about that, SE?