A vehicle has a "plated" weight. This is the gross vehicle weight allowed by law. It is not unusual for a vehicle to have a greater design weight than is permitted by law.
It is perfectly feasible to "downplate" a vehicle that is to reduce its "plated" or revenue weight. This then impacts on the licence required to drive it or the amount of road fund licence that is payable
In industry it might mean reducing the plated weight of an artic because it only carries a light bulky load, this then reduces the rfl payable
It is also possible to downplate rigid vehicles, from a 14tonner say to a 12tonner.
In our game it may be possible to downplate a Stalwart, although I really dont know how that would happen because it assumes the vehicle undergoes an MOT, how many of preserved Stollies are tested? (the comment about being over width is also very valid)
Surely the easiest cheapest and most satisfactory way of removing one of the barriers to ownership is go and take a CAT C test.
CAT C entitlement, no argument about driving qualification (may be a whole rake of other issues though to discuss with the chap from VOSA)