Put the rest into growing your businesses

That's what they currently do. All of them. That's the whole point in them owning/investing in a business. That's how they sidestep so many taxes. Aside from a few (relatively) toys and houses, do you really think Musk or Bezos keep billions on hand in liquid form or physically owned objects?

I have a friend with parents that owned their own business that wasn't really all that large. It had a net profit of maybe $450,000 per year. They paid themselves enough to do whatever they wanted to that year, and the company "reinvests" the rest. It's all a shell game to avoid taxes. They did it by buying real estate for the company to 'eventually' grow on, but just put five cows on and got themselves agricultural exemptions on taxes, then sold the land later. Repeat x100. That money from the sale could be shuffled into other 'company' assets. That's super small time. They didn't have fancy lawyers or investing agents to help.

Big, rich, asshole business does it by buying back stock, diversifying (do you really think the big contractor company wants to own a grocery store chain, or a bank wants to own restaurants?) into assets that can just be sold later to recoup the money, etc.

Owning a business is all about tax avoidance. An individual doesn't have many ways to pump up deductions on taxes, but businesses have so many different avenues that even the IRS throws up their hands at some point. Requiring an individual to "put the rest into" their business won't change anything, and god knows the economy improving is only going to help a small portion of society. That portion isn't the portion that needs help.

Also, truthfully, I'd lower your number to $10,000,000. It's enough to live on even in the ritziest of areas, in the fanciest of houses that aren't mansions, and is still more per year than the highest of the middle-class will earn in their lives.