And why only do AKL-WGN? Why not the entire length of SH1 from Bluff to Cape Reinga? Maybe include a bridge over the cook strait while we're at it, and a tunnel under the strait too for when it's too windy to use the bridge :-)
You jest, but I think we _should_ be doing that..
4 laning SH1 it's entire length (and the other major highways) is simply a no brainer to me.
As for crossing the strait, the only real barrier to building a cook strait tunnel is cost. Stuff had a write up about the possibility earlier this year, and it's pretty clear it would cost tens of billions of dollars to build, but that's not really that outrageous when you look at the cost of Waterview, City Rail Link, Transmission Gully, etc.