Such arbitrary limits won't work, especially now. For ex: WhatsApp has about ~50 employes[0]. The kind of wealth and value you can create with few people in software is very dissimilar to other sectors which (at least for now) requires a large number of people involved to be viable.
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.