I'd also like to propose in this scenario that the ownership of such companies could also apportioned out to staff, and that the government should create an environment where access to startup capital is cheaply available in all regions.

Consider how much more tax and local spending might occur. The problem with a lot of those economies of scale is that the companies and extremely wealthy individuals get quite good at reducing their tax burdens in inventive ways, especially once large enough to leverage international org structures.

And as you rightly point out upper management, are good at taking small cuts of profit from a much larger number of people, and the political leverage imbalance that this creates also really affects things (surely not one person believes an honest billionaire who gives frequent large donations to a party expects nothing in return).

Also a good chunk of that efficiency turns into lobbying and marketing budget.

I'm sure that there will still be companies that find a way to make extreme profit without large staff, and there would likely be other problems. But it's hard to believe it would be dramatically worse than the current state of extreme wealth imbalance.