The problem you are describing is revoking Citizen's United. What your trying to do is a patch job to another problem which is going to cause all sorts of unintended consequences.
First principles people, not these lazy slap dash approaches.
It's not about Citizen's United, because it's very specific to the US, while it's a global problem that rich people have too much influence.
Forget about elections and politicians, they can fund media empires at a loss to push their ideologies. No one should have that much power. They can buy lawyers effectively putting them out of the reach of the law. So many problems would be solved or reduced in intensity by taxing them.