Why add groups such as Led Zeppelin and Black Sabbath who did nothing for the progression of music. Led Zeppelin was just a blues influenced band and although Black Sabbath were influential to heavy metal, they did next to nothing in terms of innovative playing. And Queen in this category makes no sence at all since they were around after the prog movement began.
If we start a "proto-prog" section and add all of these groups to the site, what's to stop us from adding Elvis Presley, Buddy Holly, Roy Orbison and so on, then looking back even further to thier influences.
Stop taking artists you think are good and finding some loophole into classifying them as prog! Soon prog could be concidered such a broad term that it would be almost impossible not to concider any band with even the slightest unique touch part of the genre.