I've just given those cutoffs as an example, it doesn't need to be that way, they can be slower or based on the times of people actually at the event (eg maximum 20 solvers in the main event, everyone else doing solves on their own time). It would allow the main event to be more rapid, exciting and watchable, while still allowing slower people to clock times in competition and have something to aim for: I think it makes a lot of sense. (Another note: if people think they've improved their times, they can attempt to prove it to the delegate/judge before the event, on their own time again, to compete in the main event.)
Also, I think people are complaining about the time taken for events. In the UKC discussion thread people wanted longer events, but weren't able to fit them into the schedule, mainly because big cubes take a long time. It was even proposed we didn't have them in the event. This solution would allow a greater breadth of events in the main timetable while allowing people to compete if they aren't of the standard which is most highly competitive.