It would be interesting to see, but my guess is that it would be exploited to death very quickly. There is a constant cat and mouse game between search engine and those who want to "optimize" their results. Going back and staying there would be like having the mouse stand still, not good.
It would have to be a different product, developed in parallel, rather than a snapshot of the past.
I don't think it's that simple. It's a cat and mouse game but the cat can't catch two different mice. If the classic Google algorithm is significantly different from the new one, SEO that's targeting the new algorithm wouldn't be as successful with the old one which is also barely used (so no one would bother optimizing for the old algorithm).
Then make it so the new algorithm penalizes people abusing the old/simple algorithm (and since the old algorithm is simple, it should be simpler to catch people abusing it too).
It would have to be a different product, developed in parallel, rather than a snapshot of the past.