Limit the size of private ownership in companies that are not exporters

One problem with capitalism is private companies getting to rich. Such companies become monopolies or cartels and damage competition and the openness of the market for new companies and initiatives.

An obvious solution would be to create a tax or a maximum size for a company or income for one person or company. The problem with this solution is that it scares of big companies from investing in the taxing country.

Limiting only natively local companies
What if we would only limit and tax the companies that are natively local and have to be that way?

Telecom providers for example are companies that provide a service for local customers only, they dont do allot to contribute to the GDP and the export surplus, and they won't go to invest elsewhere because there is always a local need for their service. Maybe there should even be a law that they must be owned by the public through stocks.

Companies that do export and develop (like handset manufacturers) on the other-hand, should be allowed to grow and have private major stock owners.

To sum it up: companies that get their earning mainly from export should be allowed to have a single stockholder and companies that don't export and are mainly service providers or importers should be owned by the public.