Doesn't the likelihood of someone believing the "fakery" is real come into this at some point?
Just because I dressed up as a Dr. Seuss character for a school assembly doesn't mean that I have to speak in rhyme for the rest of my life. My third graders knew it was pretend.
I think there are very few guns currently being made that could ever be confused with originals. Steel barrels, modern lock parts, machine made screws, stamped nose caps, spot welded thimbles, machine made bolts, the makers name on the top barrel flat, barrel makers stamps on a lower flat, etc. Even to my half educated eye, these things spell contemporary far more than "London" stamped somewhere.
IF someone used all hand made parts and an iron barrel, then I can agree completely with these worries. But, if there is no reasonable likelihood that someone will mistake a gun made in 2014 for one made in 1790, do we really need to worry about it? Let's face it, the guns most of us build are "pretend" from the get go. Sometimes I worry that we take ourselves a little too seriously in this hobby.