You're preaching to the choir here... I'm not an A&P but am in whole-
hearted agreement that an intercom ought be a minor alteration, but
the poor A&P's are under duress of the local FSDO interpretations of
the regs and there's not much the mechanics can do to challenge that
without invoking the ire of their local FSDO inspectors with whom they
must maintain a working relationship. Seems like the aircraft
maintenance world of today has become a very, very, very different
world from what it used to be back in the mid 1990's when I first
began flying and a lot more common sense prevailed. Practically
everything you might wish to do to an airplane has now suddenly become
a major alteration no matter what, and every minor part, practically
right down to even the "decorative furnishings" in the cockpit must
now be PMA'ed, TSO'ed, STC'ed, or factory original parts only, and
getting any kind of field approval is a crap shoot.

I sure wish I could afford to build an experimental and be relatively
free from such unreasonableness.