What would happen to the economy if we'd only allow companies of 1000 people, of 100 people, or perhaps even of 1 person?
On one hand it would keep companies from completely vertically integrating or expanding to encompass many verticals. Which would stimulate the economy in one way because more people would be exposed to the profits at the top or near the top of the market. Also the increased competition might result in the improvement of various small aspects of technology that would result in better efficiencies across the whole.
But on the other hand, limiting the size of companies would make us less competitive on a global scale because of the inherent cost in being forced to buy components, as opposed to vertically integrating. Also product costs may increase, which could negate any increases in wealth among the people.
[0] Bell Labs was an agreement that Bell could have the monopoly (to reduce wiring and because of the network effect that they could take advantage of to connect the US with telephone lines) but there was also heavy regulation done during this deal that I'm sure others here are much more informed about and can correct/add to my comment with.
[^] I don't think there's ever been a "free market" nor do I think there ever could be. The US's largest economic growth happened in a "free market" in name only (propaganda a lot for the Russians) but was heavily regulated.
But this won't change. You can't change the system to protect others from greed, when people defend greed. One day they might gain from greed.
Another issue is what do you consider as part of a company? In the case of uber, would it include all the drivers or are they there on individual companies?
I guess all this comes down to what you are optimizing for: Quality of life for a median human or overall inequality. I think right now it is optimized for the former.