I've always been interested in these "lost Trek" stories -- especially the development of the scripts that eventually became TMP.
A friend's father is Jerry Isenberg, who was assigned as the producer of Planet of The Titans and worked with GR and the writers during that period. I'm going to ask him if he still has a dusty script lying around somewhere... no promises though...
Hey, so I guess nothing ever panned out?
And you know, as much as I liiked TMP, I think this would have made a cool movie. I don't like the idea of Kirk disappearing for half the movie or the Enterprise redesign (although it is interesting and kinda cool) but at least it isn't a retread of a TV episode. And it seems like it would have had a cinematic scope and feel to it, without resorting to the usual "Earth is gonna be destroyed" thing.
I hope a screenplay surfaces someday, because I'd love to give it a read.
But wouldn't it have been a retread? Didn't Kirk meet Apollo/Adonis and didn't Adonis explain who and what the Roman/Greek Gods were?