So many people want to play, but don't have much motivation I guess...
What about the following rank system:
On each map a player can have personal rank: rookie, average, pro, master or smth like that. A rank depends on time of course. Obviously, we will need some trusted ropers to set times for many maps. For example:
60.00 - Rookie
45.00 - Pro
40.00 - Master
It's just an idea and I don't know if it can boost the activity. It actually removes the challenge between players, instead you gotta challenge yourself
But on the other hand franz is right. If you want to challenge another player, play him online. And if you want to get ranks & points for maps, then beat some "edge" times.