I don't know what length and weight RV you have in mind, but I think that the Ford E-Series cutaway van chassis used by Class C motorhome manufacturers still is available in a weight rating higher than that of what I believe is the most rugged Mercedes chassis - their Sprinter 3500 dually.
Many small Class C motorhomes can be ordered/found on the higher-than-necessary weight rated Ford E450 chassis. Even if you want a small enough Class C motorhome such that the Mercedes 3500 will handle the weight under normal conditions, you may want to instead hunt for a Class C on the Ford E450 chassis so that you get the overkill durability of a 4-Series chassis that can provide such advantages as:
1. Large brake swept areas for extra stopping power under all conditions, plus longer intervals between brake shoe replacements.
2. A low rear end differential ratio for less transmission torque conversion generated heat going up any grade and for superior towing performance.
3. Overly thick steel in the frame for less frame-twist and consequent coach structure stress whenever going over an unexpected or intentional rougher than normal road surface.
4. Factory installed torsion bars in both the front and back to help with body roll. (All Sprinters may have this - not sure.)
5. A factory installed steering damper. (All Sprinters may have this - not sure.)
6. A wide rear dually stance to help with roll control on curves and in cross-winds.
The above Ford 4-Series things are of course not necessary in a small Class C RV, but may appeal to the more ruggedness minded buyer. As of yet, I don't think Mercedes offers an equivalent 4500 Sprinter. Especially note number 6. - the Mercedes Sprinter 2500/3500 chassis can be narrow relative to the height of any coach built on it.
