It's a fair question Skip, and I'm sure someone can give you a more informed answer than me. However, with the boundary limits, I'm just not sure how much ground is left to concrete over for additional apron parking. I've a feeling there may still be space to the NW of Pier 1 of T2 and beyond the existing remote stands newly completed. With the inevitable staggering of the first wave departure slots, I think before covid, a/c for the later departures of that wave were often brought onto stand after the early flights had gone, rather than busing. But that requires a slick towing operation.
Can't really comment on relative costs and who stands them.