Okay thanks for that post (sorry for accidentally deleting our little debate, that was a stupid mistake on my part.. I wish I knew if it were possible to undelete it).
Your post really helps clarify what you were saying. I guess the part that still confuses me is saying he had it "all planned out in advance" and yet he had only some vague ideas and change just about everything. Doesn't that make it meaningless?
Because he originally "planned" to make three trilogies, of nine films, including sequels. But as you got away from the classic trilogy (or rather ANH + some bonus material that made it into the second two movies with lots of new filler) it was more and more vague and such. Most of the backstory seems to have appeared in the novelisations of the movies. But not all of that made it into the prequels, some of it was changed. And what little was known about the "sequels" that he has no plans to make as he's said many times recently, hasn't shown up in the EU that I'm aware of.
I seem to recall some interview bits of him talking about "Mandalorians." That survived in Jango Fett being the donor for the Clones that became the Stormtroopers. But none of us thought they would be the "good guys" in AOTC.
Anyway, I found a forum with a lot of Lucas quotes taken from various interviews over the years. You can read them and see if it sounds like Lucas changed his mind or spelled out any ideas, etc. A lot of them I'd forgotten about myself.
He talks about the saga in general, the prequels, the sequels, the three trilogies, etc.
Thanks for your post!