I just played LineRider ( http://www.official-linerider.com/ )
and thought about a mode where you can't move, and a speed-ground or a feature to pause, go on with building the level, and then play again.
There wouldn't be any competition. It would be kind of fun to create, but almost no fun to play. It is still fun to make and play automatic levels with a harder route to get a faster time that isn't automatic.