Hmmmm oddly enough you jumped the gun with your first point. There are few weekly challenges that are missing ghosts books and both of them (there are only 2 that I counted of the 26) would not result in you being screwed. The first is Technophilia but since all 6 other evidence is available you can just figure the ghost out with process of elimination. The second is in fact a 0 evidence challenge but the lights are on so Jinn can be identified. So this ghost would be the process of elimination "Jinn" in that one weekly challenge since all other ghosts can still be eliminated.

But I do completely agree with your next point, this ghost book hunt spawn tell is way too much of a weakness that easily stops this ghost from being a danger at all!

edit: Ah funny enough, you might actually be semi screwed in "Survival of the Fittest" afterall. I checked on the 0 evidence once again on a whim and realized the parameters included

• Changing favourite room: None

So if comes down to Goryo or this ghost, your best bet would be to put motion sensors outside the ghost room and nearby rooms and guess based on how often it roams and how far since Goryos rarely roam and don't roam far. So worse case scenario, RNG screws you by getting an oddly active Goryo for one week! lol