Gib:
I actually had the good fortune to have a chat (and play with the man at County Down) who would be considered the course historian. Have you ever seen the old routing (which he just happened to find in a tube) that's under as much glass as the Mona Lisa in the front sitting room?
Anyway, that routing isn't even that much like what the original Tom Morris course was apparently. He said, I believe, that the original course would have been little like what is there today and I don't even know that any of the old green sites are still in existence, but I'm sure some must be. What I do remember him saying is that the original first hole started about where the restaurant is at the entrance to the Slieve Donnard Hotel and as you know that isn't very close to where the first hole starts now; it may even be 400-500yds distance!
Also, I really have no idea how accurate they are, but I did notice that Cornish and Whitten say that much of Old Tom's work may have been much more utilitarian than we, today, think it was--actually I think they implied much of his work would have been considered pretty bad if it existed in original form today!
To answer Tom MacW's question, I would like to see more Banks, certainly Langford and Colt and more Mackenzie. Of course I would also like to see everything that's left from original of Thomas/Bell, maybe Behr and their unique Southern Cal canyon routings. But TommyN and GeoffShac say little of what they did is left today. I did study Riviera for about half a day this summer but would love to go back and study it some more. There are things about that golf course in that particular space that are a real architectural education--not all that easy to pick up--but when you start to they are definitely a sophisticated architectural education!