from playing a few old ones and owning a lot of new guitars it really is about the wood and how it ages even with a solid body. If it is coated in so much junk that the wood can't breath and age then it will never sound like it is old or vintage. The guitar will always sound new. I personally like the feel of a nitro finish but if it lets the wood age better then i am glad i have it on some of my guitars.
The older guitars i have played all sound great and the only real difference, other than the finish, were a few nicks and scratches.
GJ i think you may be right about the kluson style tuners. They don't add much mass but let the neck wood vibrate the way it should. I think the aluminum tail pieces for LPs do the same thing as the tuners do, but there is some balance between the added metal pieces being too light or too heavy. I am sure we can come up with more factors that make vintage guitars more desireable.