Not that I disagree with the fact that this *is* a "minor
alteration," but
does the FAA consider that to be true?

Which FAA? Every FSDO is a fiefdom unto itself.

Isn't something that permanently ties into
the electrical system supposed to require a field approval?

Would that include a T&B? How about a voltmeter? A radio? Post
lights?

In some FSDO's, you're right - it's considered major. In some FSDO's
it's not. The real issue is that unless you bring it to the attention
of the FSDO, how are they going to know? You simply need to get it
past your IA at annual time.

Some IA's will ignore it even without paperwork. Most will accept an
A&P's signature and not question his determination that it was minor.
And a few assholes will actually ground your plane and make you either
pay to have it removed or get the FAA involved. A 337 doesn't save you
from this - remember how Honeck had to remove his strobes, installed
under a 337, because the IA decided they weren't legal and got the FAA
involved?

That's why it's important to choose your shop carefully.

Michael