I wish Aussies or vice versa didn't have to be alienated with such an idea, it's a real shame... because say if Germany vs Australia was in the semi-finals (and I am sure it would be), you wouldn't want some laggy racing.
That is one of the reasons Nationscup never hit it's mark; also because of timezone issues, which impacts race days immensely.
I've actually always wanted to see an A1GP style league, where ALL 30+ countries race at once, with the FO8's only (and full skinpack), since it is a very balanced car, and good with racing. Though, if you wanted, I guess you could choose different cartypes for each race, so that drivers from each country could get a chance (because there may be one fast driver in open wheelers, and one fast in FWD).
Still, timezones and times for races are the biggest issue, and there is no real way around that, other than hoping your country can stay up REALLY late/early on a weekend. This cannot always be the case, even for a country's fastest driver(s), so some countries would have to make ends meet just by filling in the blanks for time issues. That's not the way it should be.
That said, yeah you could split up different hemispheres in the first half of the season, but then that doesn't leave a fair elimination when the two hemispheres meet. They'd need to be racing against each other from the day it starts, until they are out. So I think you should stick to only a few continents unfortuneately.
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Europe being the most dominant, Aussies would surely need to be the ones driving late
But then that just brings up yet another obvious issue....