There are cooperatives (coops), were workers are also owners. But there you are not working for several companies building equity on all. But most US I knew of are no longer active. Only https://www.gcoop.coop/ in Argentina.

Oh, and found this articles: http://www.vintagedigital.net/content/setting-software-co-op and https://www.scribd.com/document/26587085/Tech-Coop-How-To

And also the Hacking Business Model proposed by Monty from MySQL fame was similar to the coop model: https://www.forbes.com/sites/reuvencohen/2012/07/25/the-hack...