Most of the problems with historic racing have occurred because of running two-strokes in the same races as four-strokes. While historic race classes are based only on date of manufacture and capacity, that is never going to change. If you look back a bit, Brice Kinnersley used to run his 250 Montesa in Period 3 against 350 Manxes and 7Rs. He was within the rules. He later had the decency to move to Period 4. There was a 125cc Bantam which was almost an RS125. And decent two stroke of 250cc will absolutely cream most four-strokes on a reasonably short circuit - that is most of our circuits. When you do that, anyone who has spent a bomb on a four-stroke will stay at home.
I love two-stroke races and I love four-stroke races. A few years ago I made a conscious choice. I sold a very good TZ350 to buy a decent gearbox for my Seeley Commando 850. Running a TZ350 is too expensive to waste it in races against four cylinder four strokes. I've only raced the Seeley a few times, but there have been two-strokes getting in my way with their different race lines. It is not what road racing should be about.