Even that "Gateway" site (3 blocks south of park) can accommodate something in the ~250-300~m range without causing much shadow there. In fact, basically the entire stretch from 4th st to 8th st on the south sive of 9th ave can go as tall as site limitations allow. Something sleek and
spirey would be nice there... maybe residential or hotel on the upper floors even... with retail frontage on 4th Street.
Let's put a new tallest there, and then build something 300m+ on the Imperial site!