====Originally I was against french fries, I worked in kitchens enough to know about the excess heat, burns, slippery floors, greased up exhausts and equipment and the hastle of cleaning the friolators. After much deliberation I feel I would lose alot of business by not offering fries.====
It seems that some sort of deep fried offerings are essential. The two items being fries and for me, onion rings. I love those rings...
How about Tater Tots?? Home fries as an alternative to potato salad? Ketchup is a great topping for those.
One item that hasn't been suggested for this topic, but many times elsewhere is a good chili...
I am currently working at a popular little place with three small fryers along with a charcoal grill. One fryer is fairly constant with fries cooking away and the other two are used for other menu items. But frankly, these fryers are quite small and for me very easy to clean as they are lifted out and strained through a fiber filter. But yes, one should be careful about splashing.
Get solid mats that cover the whole floor and can be hosed off outside. Do not worry about grease on the walls or even the vents as those dogs will create enough of a mess on their own and the most important thing is to maintain a clean appearance. Create and follow a cleaning schedule and the mess won't get ahead of you.