Speaking as a player who didn't have a choice and who wound up on a server that wasn't the one I had my eye on, I have no problem with this. RP-PVP is a very niche ruleset, and people who prefer it, I'm sure, have had to deal without dedicated servers for it before. It would be a real shame if these players all left because they were marooned on a dying server simply because of ruleset issues.
Here's what I propose. You already have the ability to open transfers from one server to another single server. I understand that coding "pick your destination from the following" into your current system may not be immediately feasible. So, if you can't arrange to give them a choice right now, move the affected RP-PVP players to an RP-PVE server (or wherever), and give them all a token or credit for a free transfer to a destination of their choice once you open up that service. I think that's a fair solution.