A meaningful "anything goes" tournament (compare "freestyle chess") would probably have as the single rule that there can't be a driver in the car. That, on the other hand, would probably remove most of the audience appeal, as it's just not that interesting to see machines compete (as is also the case with freestyle chess). No audience means no money and no money means no R&D budget. So that's probably why it wouldn't work.
I don't know when I think about how the F1 car can drive upside down it almost makes me want to see these awesome 3D tracks where cars do all sorts of death defying racing and tracks that we have seen in science fiction become possible because advance AIs are so much faster.
Maybe people would want to watch it on video or even VR so it seems like they are actually there. Who knows if done right it could be a better experience then looking at 1 piece of a race track for hours.
exDM69's note about costs is also important; it would probably be best to not allow mid-race part replacements. You submit one remote-control car and that's it, good luck.
