One problem with a short Class A diesel would be the same as we experienced with the 30' transit coaches. Because of the relatively long overhangs on a short wheelbase, they tended to have a nasty pitching motion.
When driving city transit routes, this only affected the driver, but I think it would be a major issue on a short RV.
A few years back, we saw a 32' DP at a local dealership. At the time it was about 10 years old. We test drove it and that pitching was nauseating. In retrospect, it was as well that the seller was asking over twice NADA and wouldn't budge, otherwise we might have bought it!