Automatically switch random to FCFS if there are seats left
Suppose you have a Limited Capacity lab with a capacity of 75 and one of the 'random' selection procedures selected. And suppose that after the enrolment closes, only 50 students have registered, so you have 25 seats left.
It would be nice if other students could still register for the remaining 25 seats (even though the deadline has passed). One way to do this would be to switch the lab to FCFS for the remaining seats.