For me I would love to see the kop made bigger, I have had a season ticket in it since it was a terrace and would love to see it made bigger and more intimidating, what do you think is possible with regard the kop being extended Peter.
Back in the day, the Kop was always wider with its wings, so it can go a little wider by filling in the corners but because of its low rake, the wings would be too low to see the pitch and so would need to be on the Main and SKD. It can go a little further back within guideline viewing distances. In theory, you could replicate the ARE (16,000 (?) or an extra 4,000 seats at most??) but that would put you most of the way over Walton Breck Road and new roof, structural gymnastics/ cantilever over the road/ divert the road...
I'd love to see it too but the cost doesn't make a lot of sense for a few thousand extra seats (but this is football, where extra noughts can sometimes be justified in lots of different ways). Standing that's safe (rather than safe standing). Total re-build maybe (the low rake is ok for standing but not designed for the extra weight or the number of escapes that
might be needed) but now you're talking. Dortmund's Sudtribune has about 25,000 in it for non-European games.
The existing seating density is about 0.4sqm per person and as far as I know, the current standing regs in the UK has a maximum of 47 spectators per 10sqm or roughly 0.2sqm per person. The existing seating capacity is about 12,400, which would be kind of 24,800 standing (ignoring stuff like weight and escapes - but it is easier/ quicker to escape from a standing area - subject to the capacity of the stairs). The steps on the Kop could be the right size too if each step of 560mm-ish is taken as two.
Not straightforward and you can see why people want good money to sort this sort of thing out.