It would make an already dangerous sport even more dangerous. Also, just because it may be theoretically possible it doesn't mean it is practically achievable. Think about what would happen if the driver can't approach the loop that turns the car upside down with enough speed, or within the angle range that's needed for the car to stay on it because of another car, or some problem... Basically any small mistake would be fatal.
Imagine the leader car having any kind of issue at all, thus bringing the pack to a stop. The lift would disappear and everyone would fall to the ground. With nets it might be quite a spectacle but still safe!
I hope 0G F1 racing becomes a thing in the space age (basically in space but in an arena filled with air where the only force that keeps the cars from floating is the downforce). Imagine roads at any angle!