I tend to think that most chassis cab trucks really are designed to be around town/utility trucks rather than over the road haulers. Think about it: most of them are built into ambulances, tow trucks, and similar for local use. That also explains why they are often geared low, sometimes very low.
I know that lower gears are better for towing on the highway (within reason), but pickups are rated to pull over 30k pounds now with 4.10s and with rear axles that are smaller than the C&C trucks (although if they keep putting bigger/stronger rear axles in the pickups, they'll catch up soon enough).
Perhaps the 6, 8, and 10 speed transmissions that are now becoming the norm will make these trucks even more versatile! I would really like to see a 7 or more gear manual in one. I'd buy one in a minute if they were available with a true medium/heavy duty manual transmission and in a high trim level. It'd give the option to choose cab length, wheelbase, and not compromise on anything. I'd have more capacity, heavier duty tires, and all of the things I love about my pickups could likely be accomplished.
For those of you who are thinking about fulltiming or have big families and big trailers, I see the C&C truck, properly equipped, to be perfect for that.