This is a very interesting idea that I hadn't really considered before.
Under this system would it still be possible to fire people without cause? Would there be some mechanism to share profits with the employees? Without those I think it would still be a situation where some of the stakeholders are more "first class" than others.
The links to the other pillars being the contract of purchase (customers) and the contract of employment (employees).
I guess social institutions have just one pillar (the customers).