I don't really disagree with any of that - however the GP even in Poland and other countries is restricted to smaller stadia now which suggests that at 10 rounds they are maxed, perhaps less is more and build back up from there! I can remember the Danish GP being at Parken (capacity 35k) now its at Vojens 15k?
Every promoter down under that's tried has made huge losses if i recall things correctly.
I reckon a 20k stadia would be about right - that way it could create that atmosphere and buzz - there is nothing worse than sitting in a half or even majority empty stadium at a sporting event regardless of what it is!
I even remember the 1989 world final at the Olympic Stadium in Munich and that wasn't sold out either despite it being a healthy crowd.
This might bring back some happy memories - World Final at Odsal 1985 - 37,000 apparently!
https://www.yfanefa.com/record/2011