This proposal made it through its discussion period without adverse commentary; no real need to go through it all again.
I'd say we should just act upon it. At this point what it needs is a patch.
The core libraries committee has recently approved a similar raft of missing instances for GHC.Generics.
The general guiding principle is that if there is only one canonical instance for something that can exist then it should exist. The alternatives forces people to write orphans that will collide across projects.
-Edward