I like the general idea. While I think 3 million is a lot of dough... At least for me it is... I also think telling someone who has amassed 3 billion that they only get to keep 3 million is really extreme.
One of the things about the US system that has always seemed very unfairly rigged in favor of the super rich is the tax laws. One thing that would level the play field would be to scrap the current tax laws, which are beyond absurdity complicated. Go to a very simple tax code. No tax at all for the lowest income level. Even a subsidy for hard working low income people. Several tiers of increasing tax and decreasing subsidy at higher income levels. Absolutely NO deductions! As I said, the current tax code is patently absurd.
An idea I thought of many years ago would be to mandate that the entire tax code would have to fit on one one sheet of 8.5 x 11 in 12 PT. type... Okay, okay... I suppose using both sides of the paper would tolerable. But you get my point... Right?