DEN, at an altitude 900' higher than SLC and with a similar climate, has successfully operated TATL flights under those conditions for years.

LGW is much easier to navigate as a connecting pax than CDG. However, the high taxes imposed by the UK govt (particularly on front-cabin pax ($198.70 in taxes and fees for a BE award seat)) may push DL towardds CDG to that ticket prices can remain competitive for pax flying to onward destinations.