@sometime sun,
Excellent topic!!!! . I have a great variety of mixed feelings on these issues, partly because I have seen many of my favorite ancient ruins in person and have also studied what they looked like in their prime. I use three examples; the Parthenon in Athens, Pompeii in Italy, and the Flavian Amphitheater in Italy (what we know commonly as the Colosseum).
In the case of the Colosseum, you have an issue with restoring something which has been far longer identified in its ruinous state than it ever was in its full and completed state. The Colosseum only spent about 150 years of its life in a full and complete form, until fire and a devastating earthquake damaged far beyond repair (both in extent and capacity) in the early 400's C.E. But even before the earthquake, fire had destroyed and weakened much of the marble facade, revealing the stone and indigenous tufa stone beneath. And in an interesting factoid, did you know that marble can actually burn? But following Rome's fall and the literal regression of civilization (dark ages), the Colosseum stood as a monolith of a bygone alien people. Seriously. One theory points out that the advanced ruins such as the Colosseum provided a prime motivating force to regain lost technological capabilities and aesthetic know how. It stood as a reminder of what we had achieved and lost. Local Roman art and architectural attempts in some parts mimicked the remains of ancient buildings, like arches, flying buttresses, etc. The Vatican, incidentally, stripped much of the surviving marble from the Colosseum to put on St. Peters Basilica.
So to answer one of your points, to reconstruct something like the Colosseum would deny what the gradual decay of the great monument continually contributed to civilization.
In the case of the Parthenon in Greece, they are actually in the process of reconstructing it in an attempt to restore it to its former glory. Is it a good idea is debatable. An interesting factoid is that the Parthenon was for the most part intact until 1687 when, in a what-seemed-like-a-good-idea-at-the-time decision, the Turks occupying Athens (and Greece) decided to store a butt-load of gun powder within the primary sub-chamber. And, leave it to chance, a Venetian cannonball managed to find its way into the confines of the powder cache and BAM! Parthenon Jenga! I bring that factoid up because some archeologists argue that because the fate of the Parthenon was such that it was very "unnatural," it's ok to reconstruct it. I don't think so, but there the argument is. So hundreds of years pass by and Greek and Roman history, style, and knowledge become very popular. The Greeks and British, as well meaning as they were, decided to reconstruct the Temple a little more than a hundred or so years ago. Great idea, right? Wrong. When these massive blocks were fit together 2,500 years ago, they were fit together with such precision and materials that we honestly do not know what the heck they did to make it go the way they were able to make it go. So a guy named Nikolas Balanos comes along and tries to fit the pieces together? only he "brilliantly" uses iron clamps in between the blocks. So not only does he cut into the interior of these ancient blocks, but he puts iron in them, which deteriorate and crack the marble. It is a fudge-up that archeologist are rushing to fix before the whole building collapses.
So the moral of the Pantheon is that if you do decide to rebuild it, wait for the technology to progress to a point where it will be as longer lasting than the original methods. We do not have the original methods, and what we have now is not permanent? so do not touch the Parthenon!!! You hear that Greeks? Put those tools down!
In the case of Pompeii in Italy, a major problem is bureaucracy. The Italian government and the institutions responsible have done an utterly cruddy job of keeping up the site. It is NOT preserved in the least?. it continues to decay? even with methods which could preserve a good deal of the site available. In a related, academic note, American (and almost every foreign) students are forbidden to work on many integral and specific sites throughout Italy and Sicily (Roman, Etruscan, etc.)? including Pompeii. That being said, there is ample volunteers and money willing to go into these sites, but government and organizational bureaucracy keep it from getting better. Anyway?.Pompeii suffers from bureaucratic B.S.
So essentially, we all have to get our stuff together before we can ever hope of reconstructing these valuable relics of the past.
Pompeii is a fairly huge site. In fact, roughly 70% of the city has been excavated. The rest is unfortunately under a particularly valuable portion of vineyard (volcanic soil makes for good vino) and Naples itself. But the question is why? Apparently, the land was leased because the authorities in control of the site know that they cannot take care of the site to begin with... so they leave it covered by more than 16 feet of dirt (see pic 1 below). (my pic of Via dell abbondanza, region 3, sub 2).
The areas that are uncovered are uncovered because there was such a rush to unearth it and find what have you that they did not think they would also be expected to keep it all preserved. Honestly, they should just throw some dirt over it again and leave it alone. The bare tufa and brick segmentata survive well enough, but the paint in particular is what's creeping away. Wonderful graffiti (political notices, business advertisements, gladiator praises, etc) are all fading (or rather molting) away.
Below, some of you may guess what that is a picture of. Yup? it's the ancient Roman McDonalds (popinae). Notice the osterie insignia (restaurant sign) in the back. Decayed, open to the elements, etc. (though restoration on the building is noticeable).