For me this should be picked up in due diligence and then accommodated for in PMI. What I see in start-ups is that the business owner sometimes does the lions share of the work and manages things like key contracts/accounts and/or is the main client interface. And so, should they be looking to sell, as part of due diligence he or she should have to think about who will do that work when they are gone in the target business? in the Buyer’s business? and then this can be implemented as a key goal within the IMO.