X^D I wish.
As an MVP, I would keep the editor in Nimbatus, and let the Couch Racers game import drones that had been built there.
RE: Split screen... for top-down games, I prefer a "Smash Brothers Cam" style, where the camera zooms out to keep players on the screen. Naturally, your levels have to be small enough where max zoom level is still playable.
See Stardock's new StarControl Fleet Battles as an example where too much zoom-out becomes a problem.
This type of camera makes it more viable to race from waypoint to waypoint in a sandbox arena, rather than follow a track, though there are some *great* games that handle this elegantly. My favorite is Blaze Rush. They have a conventional 'track' system, and when the camera reaches a maximum zoom level, players that are too far behind the leader are simply teleported forward. Or killed, depending on the game mode.