Good post FP. As I said before I feel it is really hard to rule out any of the important claimants with complete certainty; as you say, and as I said earlier: powered flight was inevitable.
I feel that criteria, definitions, semantics, legal and political actions all play a part in this debate and they all blur the lines to some extent. Wherever you draw the line it excludes one set of criteria. If I am expected to accept the word of the Wrights' witnesses why should I NOT accept the witnesses of other flights?! How can we be sure that anyone in those days measured "level" or any other contributory factor accurately? As you say, nowadays we demand far higher standards!
I remember reading an article in National Air and Space Smithsonian Magazine describing how Chanute was a key figure in the Wright's work as he was fully aware of developments in Europe, particularly through the Royal Aeronautical Society. No harm in benefiting from someone else's experience.
I feel that if we HAVE to single out a single person/team then no-one actually has as good a claim as the Wrights, all things considered. However, I really see Human Flight as a multi-party international effort, and I consider the hero-worship associated with the Wrights is completely out of all proportion to the contribution of others in the bigger picture.
Ultimately my opinion is the same as a Coroner's Court which cannot decide 100% on the evidence presented...."Open Verdict".