Corners: filled in with each corner having an opening for other venues to bring in equipment, etc.
Ribbons: On the NEZ and SEZ built up seating to match the same height of the existing score board.
Scoreboard: Increase to 100' on both video walls
East side: Keep the mountain view but add maybe three rows higher, to give the illusion of an increase from that POV, and I would consider adding ribbons on the east side as well. That way, ribbons on all sides except west but that gives a good natural fill to a space. Your mind will assume, more rows have been added to the east side (they have, but only three) but the view still shines.
Maybe 85,000 seats at that point?