Why not? This would be perfect for leagues, so you could have a pace car for a timed period (let us ten minutes) and then either the pace car has to go to spectate or will be kicked to spectate after set period of time.

This way, you can a full grid without the one person being sh*tbirded, so to say.

Well, we could have 21 racer slots as well then

There is apparently a way to have 23 racers.
http://www.lfsforum.net/showthread.php?t=20126