I agree with most things but I have something to add to the adaptiveness of JKD. Though JKD would definitely lead you to cross train so that you could fighton the ground and such, I would rather think that you can defend yourself against any kind of opponent that is presented to you. So even if you are primarily a striker, you could adapt to a grapplers fighting technique and still defeat him. Of course that totally depends on the person.
Like a Karate artist does not necessarily have to study other arts in order to follow JKD. As long as the artist does not limit himself and adapts in combat he is still JKD in my eyes, even if his techniques/stance/wutever are karate origin.