I've kind of come to the same conclusion on the intermediate eye relief scopes. They don't seem to be any faster for me and since fitting a "scout" rifle with detachable magazines seems to be the thing to do these days, the only reason to not mount it over the action is for ease of carry. In a semi-auto it makes even less sense because they all use detachable magazines, so unless you're going with a BAR sporting rifle, you're not carrying it at the middle of the action anyhow.
The problem you run into with most semi-autos is that it's hard to get a full-power rifle round in a semi-auto package at scout weight. You can go with the lighter rounds but then you give up Cooper's requirement of being able to drop a medium/large game animal out to 400 yards.
At some point, when I get my feet under me, I think I'll try an AR in 6.5 Grendel. I imagine the round is going to be a barrel burner, but I think it's approaching a better balance of weight and power. Of course, doing this also gives up being chambered in a common round.
Cooper would be so disappointed with me.