If you are worried about arcing wire inside the wall then why not say all wire passing through any bedroom connected wall on it's way to another room shall be AFCI protected?
That goes far beyond "is a switch an outlet?"
It has always been my understanding that the arc fault we are protecting against is the lamp cord pinched under the leg of the bed and buried in dust bunnies.
Isn't an arc in building wiring supposed to be inside a box?
If you are really saying a piece of Romex, between boxes, will burst into flames, maybe we should all be "chicago" with metal raceways.
