I think I'm on my own on this one - but I LIKE the concrete dome-with-rooflight thing they did for the tombs here - I mean, you can see what's going on and it gives a sense of enclosure which you just wouldn't get if it was left open (apart form the damage). Also, the daylight comes in really handy - and you can always sit there til late and feel what it's like in the dark if you like..
Now Midhowe is mind blowing and again, although I quite like its shelter too, that would be amazing to experience with a roof at the right height