For a truly decentralized organization, every individual should be able to do their job independently without relying to others.
I'm not sure how you would enforce that or if it even should be enforced. Didn't you say earlier that witnesses should (or at least could) include well-known companies? Those are not individuals.
When witnesses also had a worker role (pre-HF16) with a large income, several of us believed that over time, if Steem were to become very successful, each witness slot would in one way or another evolve to be a fairly substantial business (and as such an important business within the Steem ecosystem), though some could be individually-owned single-purpose businesses (others might be larger businesses in the ecosystem that treat the witness slot as a subsidiary or division).
It is certainly interesting to think of different ways this could all work. I don't think we have any "right answers" at this point.