The chassis works fine for towing. Since its introduction it has been popular as the platform for commercial vehicles dedicted to RV delivery. Even with a short flatbed, toolbox, and hitches, the cab chassis comes in not much over 6000 pounds, leaving a tow capacity near seven tons.
Problem comes in when you load it down with a house, and extend the frame way beyond the end of the factory frame. Weight of a house uses up as much as four tons of the capacity it has asa chassis, and extending the frame makes it hard to balance hitch loads across the chassis, and often precludes use of weight distribution hitches.
Often what towing capacity is left in the chassis after it has been made into a C motorhome (and this could very well be in excess of 6000 for a small motorhome on E-450) is useful for flat towing, not so much for towing trailers with heavy hitch loads.
So are you interested in finding a E-450 chassis, or looking for a motorhome built on the chassis. A tow vehicles, two very different things.