It's a good idea regarding the opening of a door into motor sport for guys on a limited budget.
The chances of destroying the car as a result of a racing incident, mechanical failure or maybe the fault of another driver is much higher than driving a boat into a harbour wall or flying a plane into the ground !
One thing to think of: when a guy attends a track day with his own car he would typically spend more time in the pits than flat out on the track.
Ten guys sharing one car would result in the complete opposite and increase the chances of mechanical failure ten times.
I still believe it's a good idea Hugh, but the aforementioned would need to be realised by all concerned to prevent the s**t from hitting the fan.