I don't think the main challenge is building this system, the main challenge is getting enough people using it to make it worthwhile.

Personally I think it should be a government provided service, not something with a sign up fee. There's actually no point at all in building this if people have to pay to use it, because they won't

Which government? Will they interoperate with foreign governments?

My point was to create something outside a specific government, with very limited information... that would require a fee or some kind of funding.

I don't think I'd trust the US/China or other bodies to trust each other for such a use case.