Well, I think that the main problem is how long can a human
endure, not how much Gs he can
resist. You can resist 30 Gs, but nobody wants to repeat the experience.
This kind of formula, I think, will take away all joy for drivers, they will be chosen among people with thick necks and able to breath in a controlled way.
Is that driving? Airplane fighters do it because they are trying to survive... I cannot imagine that "survivalist" style as part of racing. Or better yet, I can but I don't like it.
As for 400 kph or 500 khp, well... what if you put a wheel outside the "extra flat" surface? Will you break a teeth? How can you control a car that (with current track technology) is essentially uncontrollable outside the track at those speeds?
There will be other problems, I imagine. In
my field I find a few.
Pomona is an example of an hyperflat track, because
when you try to put down real power into the earth, like an NHRA dragster does, regular suspensions are not enough: track surface has to be improved. The straight at Pomona costs an eye. I quote, from the work at Brainerd track:
Laser equipment was used throughout the process to create an ultra-flat surface... After the concrete was adequately cured, its flatness was measured and found to have an average flatness factor of 98. To our knowledge, the only drag strip flatter than BIR (NOTE: Brainerd Intnl. Raceway) is the National Hot Rod Association’s Pomona Raceway in Pomona, Calif., which has a flatness factor of 104. But Pomona has transverse joints, which can create a rough ride at 200 mph-plus speeds. Instead of transverse joints, BIR’s concrete slab is anchored in the ground at half track and allowed to expand at the starting line end with the help of an expansion joint. The entire slab, constructed as one continuous concrete pour, expands and contracts toward and away from the starting line.
http://aggmanatlas.com/articles/oldarti ... eting.html
Forget about asphalt if you allow unlimited acceleration and braking: probably you'll have to move to concrete. It's not only the human body which complains, tracks also will...
Accidents will increase their destructive power. Energy is proportional to the square of speed, so the increment in chassis weight... you know the rest. Braking distance must be considered with the same approach: how far from the track should the stands be?
However, I think we should: a) give a chance to this kind of ideas and,
b) learn from other unlimited series in the past (CanAm? Or F1 in the 80's? Maybe GP cars in the 30's? What about "Old" LeMans?)
For the b) part, I think more experienced members can give you an idea of what happens when you take that approach. (Chap, donskar, Dave, we need a professional historian here...

).