This is kinda difficult if you dont tell us if you are using JAR's or FAR's.
For me, i would like to see those nice people in the USA wake up and realize that it snows! Runways do become contaminated, airplanes dont like contamination, so airlines and manufacturers should be legally accountable for these conditions!
Then you could also add accounting for line up distances.
PAXBoy, extending the runway wont solve the problem as we will just reduce the aircrafts takeoff power for the actual weight and will end up using all of the newly available length!
Old Smokey, what margins are you talking about?
Mutt.