Sudden Idea: Checkpoints? Say the round timer is at a low amount (maybe 2 minutes, depending on the map) and as players move through the map to secondary areas, time gets added to the round timer (say 3 more minutes or something). It would probably give players a bit more motivation to finish the map and spend less time fucking around at the first traps, and if they do, everyone else doesn't have to wait as long for the round to be over.
Don't know if that would be possible to code but I thought it would be nifty.