At the risk of inviting ridicule, I'm going to resurrect this thread.
(Here's hoping it takes to new life better than Ludger Brink.)
Unfortunately, no one can be told what the Ur-Willow is, without suffering a serious case of teal deer.
You have to see it for yourself... on my thread at the TFN forums, I'm afraid.
Hold on to your butts, it's 13 pages long and still growing. And that's almost entirely me talking.
(Feel free to read it and come back to comment here, though!)
In brief:
Just as there was evidently an idea for a SW Sequel Trilogy from waaaay back when, I suspect that GL in fact came up with an outline for a whole trilogy of fantasy films back in the mid-1980s... of which only the first part, Willow, was ever made.
I've noted previously that the original version of Willow was apparently much more mature in content (in terms of both explicit violence and sexuality) than the final film.
There were also considerably more fantasy tropes--Elves, fallen angels, ghosts, a trip to Hell, and even a Ragnarok of sorts in the third film.
Most surprisingly, it seems, GL actually shared his notes for the unmade Willow saga with several other writers... who went on to become household names in their own right.
It might seem crazy, but I'm pretty sure that certain extremely popular multi-million-dollar fantasy franchises owe a great debt to "Mad" Martigan and Sorsha Stormdaughter.
(Incidentally, as a result of this research, I'm forming a theory as to who will walk away with the Iron Throne... and also who will rule in Westeros at the end of Game of Thrones.)