I think keeping the number of students low would be important. With 5 of you, controlling for 20 minutes apiece, that still means each one needs to be in the air for 80 minutes. I'm not sure how many would be content to fly circuits for that long. Non-circuit VFR flight could be more fun, however – having planes constantly leaving and re-entering the circuit could prove more interesting for both the controller and the pilots.
Not to mention, scheduling becomes considerably harder with higher numbers to coordinate, unless you just pick the same time every week, and see who shows up. You could give them first-come, first-serve for controlling, as incentive to show up on time.
Some flight instruction for those in the air might be just enough of a carrot. Perhaps you could train the pilots in the air to perform the duties of the Flying Circus while the controller on the ground is learning how to deal with said circus?
And don't forget CYXS and CYQR, to break up the tedium a little. Could rotate them each week. On that note, is any S2 allowed to control at those airports, or only students from their respective FIRs?
