Here, here, Valier!
I was thinking of proposing such a threat, especially to Barrad Dash. -_-
But I couldn't bring myself to suggest it as I thought everyone would accuse me of being mean.
So, I'm going to say that if you miss 4 challenges in a row, then you will be disqualified. Your vehicle will be de-wheeled (or de-winged in Minas Mor-go's case) and sent back to its original area. Although, not in that order.
If you think you'll be too busy to continue, then we will find a new player to fill in.
Also, if Bag Endless-fuel wins the next three challenges, they'll win!

If they do, does everyone want to continue until the last vehicle has passed the finish line? Or do you want to finish it then?