Ref IIGS mentioned a bit further up - possible suspects for it:
1 - the IIGS section - obvious of course but its still an assumption
2 - workshop - noted at the time as 'friday night-IIGS' if I remember correctly
3 - barnyard - very speculative but if transported out of H&V along with IIGS make sense + fits lyrically
4 - Do a Lot - speculative but years ago a report of it with toothbrushing sounds (can't remember if teh tape box eas noted - its an obviously stolen item)
So possibly a collage type 'humour' thing as opposed to some mysterious lost masterpiece.
Personally, I think IIGS on the Dec tracklist was IWBA/Workshop, which was labelled "Friday Night (Im in Great Shape)" on the tape. I remember Vosse in the Fusion article said that the version of the Barnyard Suite he heard included workshop-like construction noises and OMP/YAMS. I think Brian's struggle here was determining how to use the IIGS-proper segment, BY segment, IWBA/WS and OMP/YAMS in some kind of collage. I don't think he ever settled on a definitive version and as far as I know no test edit of a "Barnyard Suite" exists. I submit that the crossed out parentheses on OMP in the tracklist reflects this, where Brian (thru Carl or Diane) wasn't sure if that'd be a standalone song or subtitle in a greater "IIGS collage."
I think ultimately, as the tracklist reflects, he opted to split these pieces in two. OMP already has three distinct segments including the fade (which to my ears sounds like a reworked HGS without the main vocal--certainly has the same backing vocal). IIGS probably would've been IWBA/WS and presumably IIGS proper, then it's up in the air where Barnyard would go (maybe even it was the fade to Heroes before Barnshine got swiped). I think essentially "Barnyard suite" was a working title and Brian liked the name IIGS better, so he'd use that title for this medley.
I used to think the BWPS IIGS/IWBA/WS medley is a new thing, now I think it was a vintage idea except possibly IIGS itself would go last...and also putting it right after SU and not Fire is bollocks.