The ability to lock the maximum level

So I was thinking that locking the players maximum level would be a good idea. At the moment my MMORPG’s highest zone is level 8.

Currently I have 70 player at that level and 10 player at level 9 (also I have 1000+ player at level 1 and around 5000 player at level 2).

I wish I could lock the maximum level at level 9 (or whatever level zone I have ready for them), so players would not be able to level up higher. I really would like this feature to be added so I could wait more players to be ready for the new zone.