Yup fryers are pretty much useless when it comes to catering.
Every caterer is different, with different cooking styles and different clients.
In general though.......
Lots of fridge and freezer space, smooth floors and easy routes to truck in supplies into vehicles and out of vehicles.
Lots of prep space.
Convection ovens. This is a real workhorse and one best suited to catering
Stove space
One or two 30-50 qt kettles is nice, but not really neccesary
Dish pit. For some it makes sense to rent china/glassware, for others, it is a lot cheaper and profitable to have their own service.
Hope this helps........