I think if Mark wanted to give back to the world he should do what Elon Musk is doing and start high risk businesses that can create widespread beneficial change in the world.
Starting with sports cars seems like a good plan to me. Let the people who can afford to pay a premium help fund development of the technology which can then be used in cheaper cars for the masses.
A lot of automobile technology is developed in race cars like Formula 1 many years before making it's way into mainstream cars.
I can't comment on the government subsidies though.
