Seems like more companies would be offering 30+ foot Class C's on the Ford F550 chassis. I would call this a Class C+ because it would fall between a standard C and a Super C. The ones I know of are Dynamax, Born Free, Host, & Xplorer. Are there any others? I think 30+ feet on a E450 is too borderline. The F550 gives you much more CCC, offers standard gas or diesel, with or without 4 wheel drive, much more cab room and legroom, and better engine access. That's a lot of advantages. The only disadvantage I see, is the extra length having the engine out front (and price!). Are there any other disadvantages?
Today's Super C's seem to be going to the much larger Freightliner chassis. I don't care so much about a label, I just want more choices in larger C's. A new sub class might give it more exposure and get the manufacturers attention (like the B+ did).
What is the maximum GVWR a normal license can do before a commercial or other kind of license is required?
Whether you are talking about vehicle license, or operator's license, it depends on the state and how the vehicle is used. In Oklahoma my Class D operator's permit is good for any weight RV, but in Texas I would be required to have non-commercial Class B at 26,001 pounds.
State license rules, as well as tag and tax structures, tend to fit the DOT weight classes:
Class 1, up to 6000 GVWR
Class 2, 6001 to 10,000 GVWR; 2b starts at 8501, a subdivision once relevant to EPA standards and the CAFE
Class 3, 10,001 to 14,000
Class 4, 14,001 to 16,000
Class 5, 16,001 to 19,500
Class 6, 19,501 to 26,000
Class 7, 26,001 to 33,000
Class 8 over 33,000 GVWR
DOT requires Class B operator's permit for commercial use of Class 7 trucks, a Class A license for Class 8 trucks or any tow over 10,000 pounds.
RV's are often exempt in many states, house cars in most cases, but sometimes also tow vehicles.
Relevant to towed RVs there are license classes for towed vehicle weights and or combined weights; some states may require a Class B for a gross combined weight over 26,000 (rather than for a weight rating).
Vehicle licenses are different, the DOT has little to say, it is up to the state and how they want to use vehicle licensing as a revenue source. States can do what they want, creating additional license and weight categories and deciding what uses to include or exempt. Some states require commercial vehicle tags as low as Class 2, unless the vehicle is in some way modified for non-commercial use (i.e. cover the bed of your F-250, or your 3/4 ton van is filled with seats).
Other states allow private non-commercial vehicles to be medium duty (Class 4 through Class 6), so long as the use is non-commercial, but they may have different tax structures for these classes. In Oklahoma, a 33,000 motorhome registers as a passenger car, tax based only on number of years registered. In another state, it will be a RV or a motorcoach, taxed on weight or value.
Some GVWRs exist to meet specific state tax and license categories. Within Classes 2-4, pickups, vans and cab-chassis will have GVWR options, involving no change of equipment, just the ratings, to meet state tax and license categories. For example, at one time, GVWR under 5000 was important in many rural states as a limit for untaxed farm trucks. Most states with a farm truck option have since raised that to 6,000 to match the DOT Class 1. The nominally Class 4 E-450 chassis was originally rated 14,050 GVWR, just into the class, to stay under a tax weight (14,500) common in many states from a historical weight class system.
EPA has also created CAFE and emissions categories based on GVWR that determine what GVWR a manufacturer might use for a target market.