I
    think that there may need to be a point modification to the GNU GPL that
    specifically indicates that other publically (open) licensed software
    that is included in a larger work (mostly composed of GNU GPL code)
    retains its original license even though the larger work is distributed
    AS A WHOLE under the GNU GPL.

This is true already, because it is a consequence of the way copyright
law works.  There is also text in the GPL to state this explicitly:

    These requirements apply to the modified work as a whole.  If
    identifiable sections of that work are not derived from the Program,
    and can be reasonably considered independent and separate works in
    themselves, then this License, and its terms, do not apply to those
    sections when you distribute them as separate works.  But when you
    distribute the same sections as part of a whole which is a work based
    on the Program, the distribution of the whole must be on the terms of
    this License, whose permissions for other licensees extend to the
    entire whole, and thus to each and every part regardless of who wrote it.

So if someone finds non-copylefted text whose license is compatible
with the GPL, and puts it into a GPL-covered program, then the
combination as a whole is covered by the GPL; but if you extract the
non-copylefted text out of the combination, you can use it in whatever
ways its authors gave permission for.

If this text is mixed in with other code, no one would know how to
extract it.  But if it is a separate file, as it usually is,
extracting it is easy.

If you make a significant change in that file, you can choose whether
to release the changed file under the GPL alone, or release it under
its original broader terms.  You announce your choice by what you add
to the distribution terms statement in the modified file.

This is a consequence of copyright law, so it would be true even if
the GPL said nothing about it.  Version 1 of the GPL did not say
anything about the issue, so I added the text in version 2 to help
explain matters.  But perhaps it isn't clear enough that the text
applies to that case.  Maybe I will be able to make it clearer in GPL
version 3, when that comes out (but that is not likely to be very
soon).  On the other hand, maybe explaining the situation in postings
like this one is better than making the GPL longer.