There's loads of things they can build tbh, I mean surely a few of the chain restaraunts will want to have a blast. No Burger King or KFC currently, you would think either of those wouldn't mind another site especially the former that probably would have benefitted from a move before the train station was closed for redevelopment. I mean I could live without them but most cities have and need these type places. Panda shit down as well so there's probably an opening for some form of all you can eat buffet place (or a few) in the right location. That was always busy as well.
Arcade area for the kids would probably do well again if placed with other shopping facilities.
Student theatre like the alpahabetti in Newcastle could be good, a smaller cinema that plays classic films could do well also but would probably have to be priced and marketed well. Could maybes do those things in conjunction tbf.
Could also replace the leisure centre with well errm a nother leisure centre - the old one was a bit haggard by the end but lots could be done in a new one - swimming, gym, martial arts/wrestling, go carting, five aside/bubble football, etc all good and helps attract more kids, stag dos, party's etc
Could look at the likes of an aquarium, different museum/gallery, snow globe/indoor skislope,
Endless possibilities really but obviously they need people to invest in them to do so. That gets easier with better infrastructure and attractions already there.