Cooper himself stated that no rifle currently in production had every single feature that the Scout Commission deemed desirable. He had several based on Remington actions (no controlled feed), at least one based on the Ruger Ultralight, and a few whose origin I don't know.
Some of the specs were admittedly sort of random, but they served as guidelines and goals for the most part, rather than hard-and-fast rules.
One absolute in the thinking was the ability to fire a full power rifle cartridge. This, combined with the state of the art in the 1980s, pretty much eliminated semi-auto actions based solely on weight. He wasn't opposed to semis, but they couldn't make the 3 KG. To quote Cooper,
"If a semi-automatic action were made which was sufficiently compact and otherwise acceptable,it should certainly be considered, but at this time there is no such action available. The whole concept of great rapidity of fire has been weighed and found, not exactly wanting, but somewhat inconsequential... The primary purpose of a rifle is a first shot hit,...[and] (s)emi-automatic fire does not assure this."
I won't quote the whole page, nor the part of the next chapter where he reinforces (or at least explains) some of his conclusions, but to me, they are mostly sound.
For those who dismiss the Scout concept, I would encourage you to actually pick up a copy of his book and read it. Try to avoid your preconceived notions and keep an open mind, it might be enlightening, and it's definitely though-provoking.
I've read a lot of things where people said, "Well, Cooper said this, and it's BS."
As often as not, he didn't actually say those things, but somebody read somebody else's take on what he said, and drew the wrong conclusions.