You're right that it won't happen. I'd like to see it tried though, Okore has the attributes to do that role I believe.
It's been mentioned a few times and you do have that feeling it could work but it's one of those moves you do where you have no choice (though we are close to that) or a bit of an experiment/gamble if you're in a position to do it, possibly not a semi final.
I think it is pretty likely to be Vlaar & Baker unless Baker plays left back but that isn't really Sherwood and I wouldn't want it either.