Hmm 15 teams is just too much. There'll be teams who'd be ignored totally in the edit (just like how the 20 players seasons of Survivors are) I think 12 is a great number to start with.
If they are all former racers.........we already know who they are.......right? What's the use of spending screentime on the losers?
If you watch a NASCAR race.....do you spend time looking at who is at the tail end?
If you watch the Kentucky Derby, do you watch the horses at the back of the pack?
By the way Danooky, you almost figured it out. You do have to think a bit. You could do the same thing with 13 Episodes and 16 Teams....
I do mean a standard Finale with only 3 teams.
The only limiting factor I could see, does WRP have enough soundman/cameraman crews to follow that many teams.