How about a multiple choice exam. 35 questions, 30 correct to pass then view some clips to test your hazard perception... oh wait..no, never mind.
Joking aside, I'm strongly against any sort of unlocking system. It's merely an annoyance, like others have said, I'll just wait for a 100% unlocked savegame or something.
Although, I do support allowing restriction of servers by PB times solely because I've seen it work so well in leagues.