Beachcomber,
I just tried a mirrored part copy and SE won't let you break the link. I think the only solution is to use the mirrored part copy and maintain the link or export the mirrored part copy as a .sat, STEP, parasolid etc. Of course, now you have no history on the part.
On your second comment, do you use Rev manager to copy the drawings and models to save time. I did that when I made a new revision to drawings that also now needed to be linked to family of parts members and it worked perfectly.
Kyle