A few ideas to discuss.

[Terran]

It would definitely cause metagaming and there'd be issues with time zones. A lot of people would miss out on the "Special" crates because they're sleeping when we're waking up. I don't like the idea of special crates being handed out much, but the idea of people being able to compete is always cool. How many challenges can you really do that won't be meta-game-able? Maybe Challenges could only be completed if there are 6 or more people on the server. Or maybe a staff member has to be on for one to be completed. Drastic measures, but I remember how crazy it got in NTG.