What if we ended private ownership of businesses. I don't mean ending ownership of businesses, but that every business became publicly tradeable. No more private ownership of businesses

Not sure if that would really lead to any significant change. Most billionaires "own" publicly traded companies. In fact, most billionaires became billionaires when their companies initiated an IPO.

The problem is that rich people can use their stock as collateral for huge untaxable loans. What we need to do is figure out a way to classify and tax these loans without taxing things like mortgages.