This whole idea is interesting in a couple of ways...
Authenticity judging? Back in the day, if I, or some friends of mine, built a kit they liked, we'd often build another one. Kit bashing? Sure thing. Originality was an Appearance Score item, when total points ran to 40. ...NOT authenticity...
Seems many of us liked to be able to recognize our model in a gaggle of the same design, too. Tip shapes, canopy location, wing vs fuse gear, even trike gear on what had appeared as a taildragger... NOT just different paint scheme - without which we might get dinged back then for being less than "original."
Even some structural "advantages?" Ever fold a stab on a kit Magician? ...Ever feel uneasy that the stock 1/8 balsa stab might just fold on you?
Formed bubble canopy on a Barnstormer, if you were not adept at lacing celluloid together?
Documentation? Hmmm... Seems many of us admit to kit-bashing back in the day... If we ever DID take snapshots of our revised kit- or plans-built models, how likely are they to still exist, or even be found if they do?
Now, there are many basics to remain "true" to the originals - Would you accept a sheeted foam version of an I-Beamer? That would be a place for "authenticity" scoring, and a place to express our opinion of it - but not grounds for a DQ. Technically, in most of the OTS rules, the surface appearance, sizes, moments, airfoils, areas and such are to represent the original models.
(Who would have a snapshot of a sheeted foam kit/plans-bashed I-beamer, from before we discovered styrofoam?)
Other common 'bashes' may or may not have documentation. If they do, the flier at least will suffer less razzing from the other guys...
There's been a lot of discussion, some of it heated, about what the original Smoothie, or Magician, really was. Why get steamed about that? The first Smoothie we knew of was the Air Trails plans article. The first Magician we knew of was Silhavy's design as kitted by what eventually became MidWest, or wound up in their product line, somehow. Even Sterling's Skylark differed vastly from Ed Southwick's original - one of the few things I ever heard him speak even a bit harshly about...
Today, we know about some of the original designer's original versions, and I think that's great. I also offer the idea that knowing that does not make the kit or plans versions so many of us first saw less authentic to the era. Now we can choose either version. For those who chase down the very first one by the original designer, great - that's part of what you enjoy in the event. The various forms of "Spirit of (event era)" awards give recognition to these models, which often also sport "era authentic" wheels, tanks, props, engines, etc. Now, that is going above and beyond! ...which is what hobbies allow, sometimes encourage, some of us to do.
Sure, there's an element of competition in Classic and OT - and whatever 70's or creeping-30-year event catches on. We fly them because we enjoy that side of things. We remember flying - or wishing we were flying - the great models of earlier eras. Now, we can. It isn't only competition, and the level of competition intensity is up to the individual. Some guys enjoy going BTTW at anything they do, others have different rewards and yet others like the activity for itself a bit better for the relaxed experience it is.
It would have to be a really gross abuse of the "Spirit" ideas to torque me up very tight. ...And more because it abuses the ability to enjoy an enjoyable occasion than anything else... The nearest thing I ever saw to an "illegal" Old Timer at a VSC was an equal-span AA,Sr. It was built by a great foreign flier who didn't realize that making modern "corrections" to archaic designs wasn't Kosher. There was no intent to "cheat," and he certainly flew well enough not to need any advantage from his mods. Simple misunderstanding, and accepted as such. He's been back to later VSCs and his models are spot-on the Spirit, beautifully built and wonderfully well flown. Isn't that closer to why we do this silly stuff?