It is so much easier on an airplane. If someone doesn't show up for FC it is very easy to move the next person on the upgrade list to FC from coach if they've already boarded. Once someone is in a hotel room you aren't going to call them and move them somewhere else- there's a real cost (they have to clean the room now)/hassle factor there.

FC/FS just doesn't feel quite right to me. Circumstances beyond the guest's control will often lead to later arrival times. I suspect what feels right is going to depend a lot on which person you are in my scenario though!