Something else I forgot, in the early stage performances and development of the DSOTM piece (then called "eclipse") they combined the track Obscured by Clouds and When You're In as an intro to the live sets. So the whole idea of using something dark like the OBC title track as the first song *definitely* suggests that the layout for the Obscured By Clouds album had a strong influence on the blueprint for DSOTM. I think it's AMAZING how an album under such hurried conditions could still be a conceptual piece, like Gilmour said it was.
Then again, another thought occurred that I'd been completely blind to; THE MAN AND THE JOURNEY suite! That whole thing was a conceptual live set that told a story, which must have had the band interested in concept pieces.