That'd prevent the infinite waits for a non-available file
system, and
deal with programs thinking they're writing files when they're really
dumping data nowhere.
Already supported and has been for years via the soft option to NFS
mounts. The designers of NFS figured that before Linux even existed.
We also have umount -f.
killall -9 problem process
umount -f the NFS partition
may need repeating a few times but will do the job.