Was there a reason for deploying a full AM/SM solution? With a fairly dense deployment, you could always just enabled background scanning. If you are looking at full fledged contianment, then an AM might be the better route. As for placing in the hallway, I don't see an issue with it. The Rx sensitivity on the APs is quite good and should pick up what's inside the rooms if there is a rogue.
However, as a quick baseline, you can just enable background Spectrum on the APs where needed.