Thing is, this already happens, it's just currently more in the billionaire's favor because instead of tax it's a "donation". You're proposing the same system that already exists with lobbyists and Super PACs, just more enforced. No one is going to bite that bait when they can just pay Scheister and Swindel, Attorneys at Law, to cut a private deal with the CEOs and senators of their choice, be completely unbeholden to public opinion about it, and not be required to do it again next tax season if it's not profitable to do so.

Besides, I've had quite enough of rich assholes deciding that this year they're going to donate $80m to exterminate the gays / to shut down solar startups / to arm all the cops with rocket launchers. In every situation, given the choice, they will always invest their money into whatever is most immediately profitable to them, morals or longevity be damned. This would cause our already easily-purchased politicians to be even more easily purchased and with semi public approval, as Elongated Muskrat now has a legal right to billionaire hero-worship? No thanks.

The special billionaire tax isn't an awful idea. The perks attached to it are most definitely an awful, no good, very bad idea. If something like this did get implemented it would be an absolute requirement that the investor have no say in where these taxes are spent. They may advise in certain directions, but final say should be up to a jury of some sort.