I totally agree with all you're saying about Russia (I come from one of those 19 countries), but I'm still not convinced that you can prevent the manipulation of ads by merely stating who's paying for them. I can pay for ads, I can be on the Russian payroll, you'd never have proof of that. I might just be an activist. I might just be an idealist.
I still believe that unless we overhaul entirely the way people get information these days, these matters will always be somewhat muddy. And once this particular train has departed, and I'm of course referring to the so-called freedom of speech and advertising in the social networks, it's going to be a hell of a task to stop it, mainly because you'd be accused of trying to manipulate or cover up the truth. Nobody cares where the money comes from when it pays for ads and groups that they agree on.