I think the idea has both merits and drawbacks...
The merits would be that sponsors get to advertise their products, and we get an awesome car to drive
The drawbacks would be, as has already been mentioned, bitching over whats done to the car, who drives it, what its built for, who pays for what etc etc...
however, i do like the idea, and i do think its possible, we just have to sit down and have a bit of a brainstorm as to what we can do etc etc...