Year 0: play a full season, then tear down one side (say the north)
Year 1: play a full season with three sides, giving BYU 20 months to build a new section
Year 2: play a full season with four sides, then tear down another side (say the east)
Year 3: play a full season with three sides, giving BYU 20 months build a new section that fills in the corner w/ previous new section).
Year 4: play a full season with four sides, then tear down another side (say the south)
Year 5: play a full season with three sides, giving BYU 20 months build a new section that fills in the corner w/ previous new section).
Year 6: play a full season with four sides, then tear down final side (say the west)
Year 7: play a full season with three sides, giving BYU 20 months build a new section that fills in the corner w/ previous new section).
Year 8: play a full season with four sides in the stadium with corners filled in.

Rebuild should give fans a more comfortable viewing experience. At a minimum this should include backs to the bleachers and more space in all directions.