I assume we're looking at a demolition of the entire upper level (400s/500s/suites) and a refurbishment of the existing lower level (200s/100s/10s). The new upper deck would presumably be built taller to eliminate the "tunnel vision" that exists in most of the 200 level seats, and with wider aisles to accommodate handicapped fans and better crowd flow. The current upper deck went up separately from the rest of the park in the 1920s. In theory, it could be switched out with an updated version so long as the park's foundation could take it (which it possibly could; a study done in the early 2000s showed that Wrigley was still very stout at its base.)