If Choppy’s proposed Exec Deck was to be built on top of the Sandy Jardine Stand you would almost certainly need to remove the roof. The biggest problem holding back filling the corners to the same height as the existing stands is the goal post structural arrangement that holds up the front edge of that roof, the other two big ones being the smaller goal post structures holding up the Copland and Broomloan roofs.
As I see it, you have three choices here.
1. Do you build this Exec Deck and leave the corners as they are. This adding perhaps 4K seats?
2. Do you replace the roof support structures on the three stands with longer structures with the supports (think Club Deck stairs) outside the footprint of the stands and fill the corners full height with no restricted view seats. This would add 8-9K seats. I think this may be achievable whilst retaining the existing roofs which would reduce the construction costs.
3. Do you do 2 but add in a third tier to the Sandy Jardine meaning a new roof structure to that stand but simplifying the replacement roof supports for the two end roofs. Potentially would add anything up to 15k seats, maybe even more.
My preference would probably be 2. That would leave the club able to add a third tier onto the Sandy Jardine if it wished to do so at some later time. I’d also add that if you did option 2 and wanted to expand the Bar72 experience, why not do it in the upper tier of the Sandy Jardine as it is now. Start in the middle section and expand it outwards as required. I’m sure the Argyll suite could be reworked accordingly.
A final thought on a third tier - we often complain about the away support getting prime seats in the corner. Would no-one else have them up there, out of sight, out of mind and hemmed in by Perspex and, as Henning Berg says in his post (#442) above, clever engineering of the angle of the tier?