CDL - DeRating of Vehicle's MGVWR

I would like to receive guidance on how we can properly and uniformly determine who, if anyone, and how an entity or individual may legally re-rate (up or down) the GVWR of a CMV. There are various Federal agencies that all seem to have an opinion on this process, however some of them are presenting conflicting interpretations and guidance.

My example is this: A 2005 Ford F750 VIN:3FRXF76S05V131509 (Originally made as an incomplete vehicle) certified at 33,000 GVWR is used as a truck with a cargo body for a number of years. This vehicle is sold. A junkyard removes the cargo body, attaches a dump-body and de-rates same to 26,000 GVWR by removing part of the original certification label in the doorjamb and attaching a yellow sticker with new axle weight rating and GVWR. Doing so now makes this same chassis a NON-CDL vehicle. 49CFR 567 seems to prohibit this in two ways. The first is the original sticker must remain. Second, 49CFR 567 fixes the GVWR after the first sale to a consumer. FMCSA seems to think this isn’t a problem as long as the 26,000 pound limit isn’t exceeded. With this logic, could I go buy a yellow sticker on eBay , attach it to a Kenworth T800 3 axle tractor and “de-rate” it to 26,000 lbs. GVWR? The curb weight of same is less than 19,000 lbs. fully fueled. So I could now drive this without a CDL and pull a 10,000 lb trailer? This is a slippery slope. Are there limits? What type of certifications if any, are needed? Engineering Certification? Liability Insurance?

The main reason for this request is for roadside inspectors to have a uniform standard in which to determine when a vehicle requires a CDL and when one does not. Keep in mind that when these vehicles are removed from the CDL requirement, it also removes the Drug/Alcohol testing requirement for the operator. I would ask that FMCSA define GVWR in 390 and 393 as original manufacturer’s weight rating from the factory. We need a uniform set of guidelines for the procedure in which a GVWR may be altered. With multiple agencies providing conflicting information and standards, uniformity of enforcement is impossible.