Thanks for the update Remoak.
The shift of 11/29 results in the buldozing of the big Helipro hangar for a grass runway (presumably to satisfy the gliding fraternity).
Have a look at this link to the plan:
http://paraparaumuairport.co.nz/?page_id=3
Whether or not you think an industrial estate west of 16/34 is viable that is already in the plan.
Shifting 11/29 westwards does put multi-million dollar houses along the beach front under a new flightpath. That immediately causes conflict with the RMA.
Sticking with the existing 11/29 runway avoids this conflict.
As for just having a single runway PPQ gets significant coastal onshore breezes so that 11/29 is in effect the crosswind runway.