I've been there, and its a nice place to visit, but you don't get the buzz, because you know what you are looking at isn't bona fide. It makes for nice photos, but it detracts from the sense of place.

Surely 'integrity' is the important word in all this. I get a much stronger feeling standing at the Sanctuary, imagining what it was like (to my mind the concrete posts aren't saying 'look at us' they're just an indication, to aid your thoughts) rather than a kind of pretence with modern stones. As mentioned earlier, that does feel a bit disney to me.
I don't like the idea at all.