Derek Lyons wrote:

And where precisely are these two 'extra' Soyuz going to
come from?

An excellent question that goes to the heart of the matter.

I'd be willing to spot them one extra Soyuz available on
fairly short notice, which would get three people down while
leaving the emergency life-boat on ISS. Russian boosters
and hardware in general are notoriously rugged and given to
rough-and-ready response. But that assumes that they're
available to respond rough-and-readily.

However, how soon after an initial emergency Souyz launch
could Russia get another Soyuz to ISS to return an additional
three people and leave the station with three on board?

Krikalev's concerns are worth thinking about, but I'm
not sure where the answer will come out.