As for the suggestion, I find it quite interesting actually. I'm already getting some ideas on how that could be tweaked into different directions. And stuff.
I love the 5x5 x2 idea, however I'd recommend slightly increasing the limits, to eg. 6x6 or 7x7 (x2) -- might be more suitable for the Canyon environment. At least for those who don't want to use 3rd party tools to force-connect or overwrite-build the track.
Up and down Build a 50 - 80 seconds long track in which the car reaches the highest and lowest buildable height, one of them twice, with the other between those two. In other words, there are two possibilities -- From lowest height to highest height and then back to the lowest one, or, inversely, from highest to lowest and then back to highest. The car does not have to have contact with a surface while at the highest (or lowest) buildable height (i.e., it can be mid-jump). Lowest buildable height is just above water (not ground level!), highest buildable height is obvious. Optional regulations: No boosters allowed.
Rated aspects: Creativity of how to get the car from bottom to top (and vice versa), gameplay.
Intertwined Build a track in which the track resembles a knot -- it intertwines itself via overpasses and underpasses, creating a seemingly chaotic spaghetti mess.
build a map with only one slide (min.30sec)
build a map with an excact number of blocks (10, 20, 30, whatever) start, finish included
build a map with onlay 3, 4, 5, 6, 7,... different blocks, start, finish not counted
or the classic version, admins give some blocks and you have to connect