The Carlaw Park vs Mt Smart debate back in the day was again using Brisbane as a reference with the Broncos moving from Lang Park which was in need of work to ANZ. We seem to be always copying Brisbane / Broncos except for the winning consistently bit.I think Suncorp to the City is more like Carlaw Park. Also it was a league ground in the first place and therefore was sacred (don't mention the graveyard bit!!). Mount Wellington disagrees with me but they missed a chance with Carlaw Park. All this conjecture about a stadium on piles over the wharf sounds too expensive to me.
The places I reckon need to be on rock hard soil, so that is either railways land like in Wellington, Victoria Park or Tank Farm.
At the time the Broncos were getting huge crowds at ANZ so we copied them on a smaller scale. Of course those crafty Aussies look to have been rebuilding Lang Park into Suncorp during that time.
To me the CBD makes sense as all of your public transport needs to head in and out of the city to get the workforce in and out of the city throughout the week. So 40-60k on a Friday night or weekend shouldn't be an issue.
On your point about building on the wharf. Murray Deaker made that comment last time this came up. He said something like "you can't grow grass on concrete" or something about the water underneath. I made that comment to my brother in-law who used to be a green keeper and he seemed to think it wouldn't be an issue as they'd be able to control the environment a lot better.
I can't get him to clarify on that as he's now my ex-brother in law. But that's a story for another day/thread.