This was the topic of a piece to the current Pop City:
http://www.popcitymedia.com/features/arena0812.aspx
I wish it could be repurposed, but I don't think it's current location is ideal. My idea (yeah, nobody asked but I'm gonna tell you anyway!) is to make it a massive, high profile Farmer's Market further from the Strip (so as not to compete) to showcase SW Penn's farms and dairies. It could have a small Rachel Carson-y spin to it--a small, permanent exhibition on local produce and sustainable food production and maybe another demonstration area for cooking that would attract visiting chefs. The retractable roof would tie in nicely.
Food is not a Pittsburgh preoccupation and I'm pretty tired of hearing that all we are known for is chipped ham and french-fries-on-sandwiches. The restaurant scene is not up the standards of a city of our size or heritage (and really, this is important when attracting talent from around the country), so if the Mellon Arena could be put in the service of this, I think we'd kill two birds with one stone.