HighKick
Master Black Belt
Most schools do exactly that.So if a sensei is going to require patience for rank advancement he could do it by simply having minimum time requirements for rank advancement. Before you can advance in rank you have to be at your current rank for a minimal length of time, within reason. Before you can be a black belt you have to be a brown belt for a reasonable minimal length of time, once you've been a brown belt for that minimum length of time you should then be eligible to test for the black belt.