Hey Firko, how old is that rule book of yours, it certainly isn't 2008. I run a novation swingarm on my 1978 CR250 and am rapt in it. I tried a Fox replica, and due to poor workmanship I had to modify it to stop it hitting the frame and also ream out where the bearings fit. I pissed that one off and tried a Thor arm. The fact that one side was 9mm longer than the other causing the wheel to sit at a 45 degee angle didn't thrill me too much I'll tell you, especially when the guy who made it reckons it was fine, I must have bent it putting it on. How the fork can you bend a swingarm. I will not use either again.
Next try was Novation. I got a banana swingarm for my CR250RZ, bearings pressed straight in, slipped on the bike beautifully, shocks and wheel fitted straight in and it works great. Also, it is totally legal for the Evolution class. I also fitted Novation straight arms to 2 more CR's with the same results.
There is absolutely nothing in the rules to state you can't fit a new aftermarket swingarm to an Evo bike, nothing. By that logic you wouldn't be able to do anything to your bike. Rule 18.7.12.3 does say "all components will be of the period the machine was manufactured" which means if the technology was available at the time then it's legal. It's silly to say it's legal on a Honda but not anything else.