I don't know whether nitrogen alone versus plain old air would make that
much difference in supporting a fire. As I recall, the heavies have blow out
plugs in case of a hot brake, so the plug melts and lets the air (nitrogen)
out before the tire blows.

On our base they fill the KC-135 tires in a big steel mesh cage- kind of a
reminder of what could happen if it let go.

Reminds me of the time a line guy in a local airport filled the air bottle
for a Vendenyev engine (they use an air start and not an electrical starter)
with oxygen rather than compressed air. The resulting fire burned up the
whole plane. The initial start-up must have been something to watch-
ignition on, engage starter, two blades, .... then kaboom!

At least it was in a Wilga, and not an aerobatic plane. It was the aviation
equivalent of Darwinism- ridding the world of ugly airplanes.