Lots of ways to do this. But overall the idea isn’t that the only investment you can ever make is in the company you work for. What could happen is some shares are public and the rest are held by employees. Employees would own enough to reserve more power in decision making so that the employees have greater say in direction of the company. It also means private Business can also be private. Just make it so that if any company wants to go public they should be employee owned or similar.