I have read through the document a couple if times now and also spoken to the person responsible for running the consultation. To be honest it seems quite reasonable to question these categorys, aimed at people abusing the system to save operating costs. (Just like the "Fire Engine" category being restricted when the limousine companies started abusing that one.)
In principal it is saying that vehicles that can be tested, should be tested. I can't see a problem with that.
It does seem that preserved vehicles have not, so far, been considered, because it is aimed at stopping modern stuff using old loopholes.
The change seems to be in the plating and testing regulations rather than the construction and use regulations so there is no proposal to test a 1960s vehicle to modern standards. For example, fitting of rear and side guards are not required for vehicles made before 1.1.84 so a 1967 Bedfoerd RL can't fail a test for not having them fitted.
I have sent the person responsible for this consultation (Robert Newman, vehicleroadworthiness@dft.gsi.gov.uk, 0207 9446575) the link to this thread, he would welcome any sensible contributions to the consultation process. Remember it is still an active consultation, the best thing to do is present constructive responses.