I'd think a diner would do real well now that there are some dense night life options South Campus Gateway / Campus Area and Park Street, they sure get a pretty good business at the gyro carts when the crowd heads out, I would have to think it is only a matter of time before something like that would open, but I've been wrong before.
In the past steak and shake had served the role somewhat (although having two floors was the dumbest idea ever, never once had I seen that floor used, even if the place was packed, and sometimes they did have quite a wait late night and had a bit of that hang out at the diner vibe - although my jersey friends would kill me for saying that, especially since there were no disco or v fries on the menu)
Up in Cleveland's eastside, Cleveland Heights, if anyone knows the area, the owner of Big Fun , the weird toy store in Coventry bought two diners, shipped them in and refurbished and connected them, but failed to do much business (on Lee rd) and sold them, someone else tried and they also failed and closed, think they are vacant now. The problem I always thought was that they were a bit gimmicky, aiming at families who wanted to live in the '50s for the day, down the street there is a 24h institution Chuck's diner, which has absolutely horrible food, but still looks good when the bars closed and you get the great diner mix of patrons in there, just be careful as there is often puke in the bathroom on a Saturday night, kinda miss it sometimes though.