In an ideal world, you'd have decent highspeed train services up to Kumeu, Kaukapakapa and Wellsford (ideally Warkworth, but the exiting lines don't go particularly close) so that those places would be viable commuter suburbs. Same with Pukekohe and Waiuku in the other direction. Smart urban planning would also involve having quicker ferries going to/from Gulf Harbour and Beachlands.
Actually I am not so sure about this. Train service yes. Light Rail yes. Even Heavy Rail and Light Rail operating on a common gauge to maximise opportunities. But high speed to Kumeu, Kaukapakapa and Wellsford? Population not there to support it.
It is even questionable whether the population is there to justify HSR between Auckland and Hamilton. Certainly, I agree that an express rail service with a travelling time around 75 minutes from central Hamilton to downtown would be desirable and possibly doable and justifiable - maybe even with a stop near Manakau City and AKL airport, along with new rolling stock and a significant upgrade to lines. But the infrastructure required for a proper HSR service is IMHO well beyond NZ's needs and affordability at present.
100% agree with you, currently Auckland has a western and southern line. All be it the southern line also has a "Eastern loop" which doesn't even go to East Auckland, the Onehunga and Manakau branches.
Ideally, what Auckland needs is
Western Line: As today ,Britomart - Swanson
Inner Western Line: Britomart via Pt Chev, Te Atatu, Westgate, Kumeu/Huapai with selected and peak services extending to Helensville.
Southern: As today but with selected and peak services extending on further into the Waikato.
Eastern Line: Britomart to Glen Innes then branching off towards Pakuranga, Botany, East Tamaki and onto Manakau
Northern Line: Britomart to Silverdale with selected and peak services extending to Warkworth.
What you could then see is something like this.North South Line
Manurewa > Silverdale via BritomartEast West Line
Haupai > Manukau via Westgate, Te Atatu, Pt Chev, Briotmart, Orakei, GI, Pakurang, Botany, East Tamaki.West South Line
Swanson to Manukau via New Lynn, Britomart, NewmarketSouthern Loop Line
Manukau to Onehunga via Mt Wellington, Britomart, Newmarket, Greenlane with light rail from Manakau to the airport.
This has taken less than 10 minutes to think of but it's about trying to connect a spreading Auckland with rail at each key growth area and ensuring transiting options exist . Completely not affordable and not realistic, i'd say this is easily $30-40B. Imagine the fuel tax on that.
This is not aviation related at all except the fact that whatever Auckland does they need to make the airport connection however it looks a priority. In my opinion
and experience that doesn't have to be to the doorstep provided it gets you close and allows you to connect onto a regular, comfortable and convent link that does. This does not
mean getting on a bus sitting in traffic though.