not enough lifeboats for everyone.

If you have fewer lifeboats than people on a station, you then have a
very serious "human" problem of who gets to decide who gets to evacuate
and who gets to die. Soyuz having individual seat liners does provide
some "guidance", it is those who have a seat on the available soyuz that
goes down.

But If you have 3 seats on the soyuz, and only 2 or the 3 are present
(third stuck in different module and unable to reach the soyuz, then you
have the problem of who gets the 3rd seat even if the liner isn't
matched perfectly).

The only solution to this issue is to have a station with sufficient
redundancy and either racetrack layout so that failure of one module
still permits circulation across the station, or airlocks at both ends
with emergency eva suits to allow transfer to the safe side of station.

You also want to have much redundancy with regards to ECLSS and
food/toilet. Right now, the USA ECLSS "core" (aka: the O2/N2 tanks in
Quest) are attached to node1 and controled by Destiny. Someone stuck in
Columbus would not have access to this if there were a fire in either
node1 or destiny.

Perhaps the last shuttle flight to the station should install a modified
PMA device on node2 which would allow a soyuz to dock (even if
manually). This way, rescues would become possible once the shuttle is
retired and the USA has nothing to replace it.