I can see the argument against new classes or more classes, but isn't the aims of the SCTA and others to give everyone a chance to compete. To keep it fair, you have to run against vehicle which are comparable. I don't think the increase in the number of classes devalue the racing or the records, speaking from an observer point of view.
It's good that almost every kind of vehicle is accepted and has a class, as long that safety norms are respected. Personally, one of the thing I like in land racing is diversity. I don't think it's really good to exclude people from this sport on the ground of 'non conformism'. I may be wrong.