I remember reading (possibly in the Genesis biography) that one idea for the follow-up to SEBTP was to adapt the story The Little Prince by Antoine du Saint-Exupery. If I remember rightly it was Rutherford that was pushing for this. In the end of course Peter's own Lamb story won out. Do let me know if I've misremembered this!
Banks' Mad Man Moon has always strongly reminded me of the Little Prince story - in both setting and theme. I used to think that before I ever read that they'd considered adapting the story. I'm just wondering if Banks still had the Little Prince in the back of his mind at the time of writing ATOTT. Or maybe he'd started writing it a few years before? I don't know - I just always thought it was interesting. TLLDOB would certainly have been a very different, more romantic and lighter album if they'd gone down that path - perhaps not dissimilar to how ATOTT turned out.