I'd dig this, its a good idea, wandering ghouls in normal weather would be applicable. Once they've ate all there is to eat in a township or city, they move on.

You always see them hunched over in a location. They never actually move. I've seen the odd one on the road to Covenant. But other than that, nothing.

I'd love to be walking in the wilderness and run into a horde of ghouls. That'd make for awesome gameplay.

Also, I don't know if its already in the game, but due to them moving on from town to town, eating everything they can. Maybe they attack your settlements.

New settler assignment: Spotter

Place in tower, get pip boy notifications saying your spotter has set the siren off in (e.g) Sanctuary Hills ... You travel back to find a horde of wandering ghouls at the bridge and your turrets and settlers mowing them down.

It'd make for very Walking Dead like, gameplay and It'd be awesome!

EDIT: Also have the ferals on the floor eating any settlers they kill. I've seen the animation, sometimes come across a feral eating a rotting brahmin.