If Greece could manage to rebuild the Colossus of Rhodes, would it become a world heritage site?
Not perhaps a "good" example, since no one really knows what the Colossus looked like! But there are plenty of examples of reconstructions on the "List" already (even putting to one side the example of Warsaw where the reconstruction itself was regarded as having OUV). Many were reconstructed before inscription and some since - but, apparently the sites are still regarded as having OUV in both cases. We have a number of them on our Connections - e.g Anastylosis, Damaged in WWII, Damaged by fire since inscription.
When one tries to "unpack" the concept of "Authenticity" it is very hard to pin down and contains a very large "cultural" element. It has long been recognised that structures in areas of the world where perishable materials such as mud and wood are used are always going to require frequent reconstructions in order to repair the damage of time and of fire -and such reconstructions have not always followed the original. The reconstruction of the Buganda Tombs in Uganda is an example - if a wooden and grass building can be reconstructed and still have "value" why can't a stone one?
And some of the buildings we "think of" as being authentic almost certainly are not - very early photos of Borobodur show that a large part of what we see has in fact been reconstructed - similarly with Bodh Gaya which I recently visited. The Archaeologists of the time may have done their best but almost certainly have "failed" to maintain "true" authenticity.
If Bamiyan had been destroyed 100 years ago and had been reconstructed then would it have "lost" OUV? But there are other sites on the list which were reconstructed in the past.
And what about e.g Abu Simbel - yes, the original statues (albeit cut into blocks and "stuck" together!), but now located in a "non authentic" position, sitting in front of a hollow man-made hill and overlooking a lake which shouldn't be there!!! I am not saying they shouldn't have been moved - clearly they should - but we make compromises on "Authenticity" all the time.
Modern techniques based on 3D analysis of photos could permit the Bamiyan Buddhas to be reconstructed as near "perfectly" as anyone would ever be able to tell. Since the location and surrounding landscape would be far more "authentic" than that at e.g Abu Simbel such a reconstruction would surely have as much "value" as it does?
There is of course tremendous debate among archaeologists about "Authenticity" and the current "anti" rebuilding view regarding Bamiyan may well reflect a "hardline" view about it which won't necessarily always be in the ascendent. I suspect however that other matters come into play also regarding the current unwillingness to commit to a reconstruction. There are more important things to do in Afghanistan (!!), who knows if the Taliban will ever get back and destroy them again (but no one would dare even consider this possibility publicly!!) and there seem to be tribal issues between Karzai and the locals who live at Bamiyan (who are convinced that the Afghan government is against their minority)