We actually use the opposite strategy...we book it KNOWING it is 50/50 it will go down and turns into an any attraction FP+.
Basically if an attraction is down or planning to be closed for unforeseen reasons last minute during your FP+ window your FastPass turns into a "Any Attraction" FP+ (there are obviously a couple of rides that are excluded)...you will typically get an email or it will show in MDE...After all these years how did I never know this? I thought you can just come back to the attraction later. Are you saying that if an attraction is down you can go to any other attraction during that window and use a FP+? If so, nice.
Basically if an attraction is down or planning to be closed for unforeseen reasons last minute during your FP+ window your FastPass turns into a "Any Attraction" FP+ (there are obviously a couple of rides that are excluded)...you will typically get an email or it will show in MDE...
We don't FP Peter Pan. It kills me, but my 71-year old mom loves Tinker Bell so the queue is one of her favorites. The things we do for the people we love, eh? LOL