If it were an exact copy, I'd feel fine or apathetic towards it. If it used any non-natural, 20th century materials different from the original prototype it would be a phony gesture of deception and would incur my wrath. If it was trucked in a flatbed truck and bolted together, it would also incur my wrath. I wouldn't build an exact copy of a historic building like that because it wouldn't fit my use, but it wouldn't be ethically disagreeable. There is a purpose to prolonging historicism and tradition in architecture in the same way there is within clothing or watchmaking, but it has to be true to the original method of its creation and that specifically means materials. Two hundred years from now, a perfect replica would still age to match the same natural characteristics as the original, so it would still maintain (and gain) value from that expression of age that we're taking delight from looking at it now. A replica that used rubber shingles wouldn't. You're being dense.