How does moving 11/29 westwards put the flightpath over houses that were previously not affected? I haven't seen the plan, but moving a westerly runway further to the west won't do that.
I still think it is unnecessary. There are plenty of single coastal runways around the country, they seem to manage OK.
You can't establish an industrial estate on the western side of 16/34, that put it in amongst residential areas.
Associated operated the 421 for quite a few years from the mid '80s. They eventually replaced it with a J31 leased from Origin. The J31 lasted a bit less than a year, from memory. There were some operational problems, and it was never well advertised or marketed. I think it stopped in 92 or 93.
It would probably work well now, the catchment area is a lot bigger these days, and many people north of, say, Tawa would much rather drive to PP in the morning than struggle into Wellington through all the traffic. If it was marketed properly, it could work well.