/buyrank ( Insert permissions group ) Targets X rank in Permissions Checks iConomy money. If Equal X money + take away X money Performs a add user group command through console. User is now moved into the group User has been given -X money from iconomy. Yes it does mean the user will be able to trigger a command to execute commands via console. but this will only happen if they have the required amount of cash in their iconomy. Also maybe a way to switch through their ranks? If that's too much then forget it.
Instead of using a command for this you could use the plugin serversigns for it. It will allow for buying the ranks for money and the command will be executed by the console instead of the player itself if you set it up with the right command.
