Well here's some things that I think are cool...Then again I'm stupid so they're not all good ideas
Cave social
What you do is make a nice build with multiple rooms for things like bar, pool, workout for fatti's, and rooms for people to build in. What would be cool about this is letting people start out with a smal 16x16 room and then you coul show off and compare building styles. Then if they're good they can move onto a VIP room that's bigger and possibly some specail privliges to secret roomsl. So the goal would be people hanging out talking and building diffrent rooms and showing off or learning build styles. Also you said your working on ramps so this would suit you.
Stuntplane competition
You make some things like rings for planes to fly through and do stunts around, have diffrent things like seeing who can land a plane on a really small takeoff strip. Like start it out like a 16x72 then a 12x32 and then down to an 8x16 and such. Best part is if you host it weekly you could have a build day where people can try to make courses that would go for the weekly competition or practice runs. Then you get judges to say the run and makybe even have someone record the whole competition and upload it to youtube and link it to a forum topic.
Mirror's edge
The title is pretty much what it would be. I've seen some Mirrors edge builds and servers but it seems it's either: one team's overpowered, too short of a run/build, or the build is just plane crappy. You could make diffrent parts to the build like Freerun, climping, chases, and missions. For freerun its just a part of the city where you can.. freerun, try to get to the highest point of the build, race around with your friends and so on. Climping would be that you start off at the bottom of the build and use various objects to climp up the buildings and maybe to some goal spot. Chase would be a sepret minigame where obviously the cops would not be able to freerun but have a gun and try to kill the runners, the runners don't get a weapon other than fist but use agile player to run away.
City chase
A game where there would be your traditional capture the flag, except you have one really big map, tops of very tall buildings, and you rocketjump to get around. What would happen is each team would be on an oppisite part of the map where you use te TF2 flag so you can still rocketjump, then of course you can try to play offencive and take the flag or play defensive and try to kill the enemy flag grabbers.
Street racing..blocko style
What would happen is you make a somwhat level city build with many diffrent roads and shortcuts. There are two teams, one are the racers who try to win the race, durr, and once they make it to the checkerpoint they still have a ways to go. From there they would take (rob) the bank brick for the cops and robbers varient and once they have the money you have to get away on foot. Now the other team is the cops who for the first half of the race only use the EMP that someone made while back and the cops stay on the tops of the buildings. However for the secound half the copsc can chase after and try to jail the racers. The first one to bring the money to the safehouse wins.
Poll