1960s era Congress already created CFC, PFIC, FBSCI, FBHCI laws which ensures that compliant Americans can't have passive offshore companies to defer taxes indefinitely. You looked like you were on to an original idea but your grandparents already thought of it. What you suggested still requires your non-compliance and the opposite of perfectly legal.

Those laws put your offshore earnings from US connected entities right back on your US personal income tax.

Most of these regulations are undermined by not having a passive holding company but an offshore company with additional business operations.

The theory being that the company would be funded on that margin and by knowing the cost to set it up and the rate of return from the marginal cost, you could put together a plan to build it and grow it.

A non-US citizen could set up a corporation in a zero tax jurisdiction and allow partners to come in and keep diluting their share as long as it remains over 50% .... or a few other stipulations when it got over a certain number of members. but then adding additional property to this gets murky, and the non-US majority beneficiary has claims on the direction of all the property.

If you are functionally able to control it then then US courts will undermine it anyway and levy a big tax bill on you.