Without safe standing increasing attendances then within the footprint then for me, we are at the sweet spot. We also have to consider the appalling transport links to Anfield that are extremely unlikely to improve.
Personally, I think an extended ARE is about the limits of what is possible.
We may well be at the limit of what is financially feasible (but not what is possible).
It is possible to redevelop the SKD to the same capacity as the Main. Is it feasible? I doubt it - especially when you consider the properties behind and the geometry of the existing stand and the likelihood of needing to demolish and re-build the upper tier. Given it already has plenty of hospitality seating, where's the extra income going to come from to make it all feasible?
Solve that conundrum and then you might possibly consider how to get people out of their cars.