My client pays for me and are not willing to have me replaced by anyone else. I have tried numerous times. I have seen a lot of people do contractual replacements where they hire people has employees and place them as contractors in other companies. That seems like a fairly stable revenue model but the goal here is to provide software as a service rather than the placement of resources. I guess one option could be to work for a startup and try to get some stake in the company fairly early.