I think it has more to do with Animals as the intro and outro of Seventh Son is acoustic, just with Pigs On The Wing. Also, notice how the 'Seven deadly sins' poem and the Pigs on The Wing tells about the same situation, in which the trip will begin and at the end, both verses say that it all ended on that story, but the moral of the whole thing will keep on repeatin on and on and on, as in the ouroboros figure related to Moonchild. That's why I think Steve was mostly inspired by Animals than The Wall, not to mention I think I read Steve saying Animals is his fave Floyd album.