But sorry to say the flaw I see in your analysis is that you don't appear to consider the case where a new branch appears (which was formerly hidden by network disruption, propagation delays, or intentionally) which has a sufficiently different set of witnesses from the "current MC" which any particular node analyzed.
There can't be a branch with substantially different set of witnesses. There are no forks by design. This is because the stability point can't advance without support of the majority of witnesses named in the previous stability point. And there is a rule that the set of witnesses in new units should differ from the witness list at the stability point (specified in the new unit) by no more than one mutation. The rules are really tight, you can't go too far from the witness list at the stability point.