Re: Adding a pickup cover...possible? Good idea?
I'll answer part II of the title of your thread: QUESTIONABLE IDEA. I went through a covered pickup phase, and I found that they put a dent in the tone, especially with lower output pickups ('59, A2P) in the neck. I've directly compared the '59 in the same guitar, covered and uncovered. It was muddier and blurrier with the cover.
It didn't affect the higher output pickups as much (Custom, Distortion), in fact, I think the distortion sounded slightly better with the cover. ALSO: nickel covers are subject to tarnishing if you're a "moist" player (have fun with that one.) Chrome doesn't tarnish, but it looks cheaper to begin with.
I'm back to open coils.