At the end of the day the Rules are the Rules and once you sign the bottom line you are agreeing with them whether you like them or not, they are written in black and white, end of story.
Personal, for one off national titles, I think the more orginal the bikes should be, as the manufacture made them in the day, barring tyres, cables, levers, handlebars and grips as these are true consumables, but only comparible to the orginals' should be allowed. The other components can all be remade/built to the same standard as orginal. True Vintage racing.
The scrutineers I assume have a hard enough job without people turning up with something that can be protested. If you keep your bike as close to orginal as possible and race in the Nationals then good luck, you'll be the better for it and if you podium I bet the wine will taste even sweeter.