A fifth wheel can have pretty much any option that a class A can. I am on my second fiver and both have slide toppers. I don't understand your statement that they don't have them. Fivers can also have auto leveling, washer/dryer, dish washer, powered shades, fireplaces, etc.
2012 Ford F-350 PSD SRW ** CURT Q24 ** 2018.5 MONTANA 3791RD