I suppose that any investment will be an improvement. However, my vote would be to: rip the thing down, build a western plaza for GABP and incorporate the rest of the area into the Riverfront park, and build a new Arena + hotel in the Horseshoe complex.
This could then become a more permanent home for casino centric entertainment (i.e boxing, concerts, final four(s), touring shows like circ du soleil) also be a headquarters and/or ticket center for a theater district/scene that includes the Aronoff and Taft theaters and others.
I played with this a long time ago (probably mentioned it before). looks something like this: