First a CDL is a commercial license, not a RV license, the additional restrictions such as drug testing, health checks, etc, that would not be welcome (or needed) in RVs
Now a number of states, and my perception is the number is slowly growing, do have a non-commercial license that is required for RVs over 26,000 lbs. The testing for this license is more intense then for a "car", but doesn't carry call the restrictions a CDL does.
My belief is that this "large RV" license, with required testing (and training?) could be a good thing.