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It would help if this was a car culture, but it's not.
U.K.  is one of the top car cultures in the world.

Also, people here don't have a lot of free time.

Is this idea for locals or expats? If locals, the countries that you list are rich Western countries where people have discretionary income to blow on hobbies. Car here have had 100% import duties (now decreasing). Of the relatively few cars there are, most are owned by government or business, which employees use as a perquisite.  It is rare to see young people driving. I've never seen a modified car, so you don't have that hot rod culture. You wouldn't believe how slowly cars are driven. If you were doing small displacement motorcycles, that might get participation. If it doesn't cost much.
Have you looked at richer countries like Malaysia, where they have a F1 Grand Prix, or Thailand where they are having a MotoGP next year?

The idea was mainly aimed at expats at the moment, hence posting it on Expat.
for anyone to get a vague idea the type of racing, search - brisca stockcars on google.
that is they style in the richer western countries, but the idea here could easily be started with much cheaper self built vehicles, as it was way back in 1957. The self builds could easily use motorbike engines, as some current formulas run these but alter it to have a prop shaft, like A LOT of the motorised tricycles here use!

It's good idea but u need to consider carefully. It's like goft in Vietnam. There is a big area and they have to pay much money to join the game so it's suitable for foreigners or rich people. U won't find a good place to open it in centre. Maybe in Cu Chi, Hoc Mon, Binh Chanh district. It takes 30 minutes from center.