Okay, so I have an idea for a new starting for race maps: It works like this, there dumpsters in front of you unmoveable because of Teleporters, after 30 seconds a Grav Lift respawns; sliding the dumpsters out of the way for you so you can go and race.
Yeah, there are a lot of maps that already do that. What you thought of is called a timed map event, and it's not new at all.