Random teleport plugin are doing lag very much because you can teleport a place where nobody has been before. I think this problem can be solved by opening teleporting coords before teleportation. I mean there is a plugin named worldborder. It can generate map like someone walking there. When random teleport select coords, plugin will start to generate around of the coords but frequent will be low. After generation maybe 10-15 seconds later player will be teleported there. It can be good, can it? Sorry my bad english. I hope you can understand me.