Given the lack of numbers and capacity with RNZAF airlift and the timeframes on getting a replacement, I wonder if getting a pair of C17's (soonish) would be a good idea? Yes they would cost a lot, but it would give NZ the distance and lift to cover operations of current size, allow the use of the Hercs in utility roles for longer periods, reduce the strain on the C130's and buy time for their eventual replacement.
The more I think about this the more I reckon the Govt of the day should go ahead and bite the bullet and order two now/soon. It would be perhaps about a $1000m investment but it would be a 30-40 year investment, which in that context is certainly affordable and payment could be spread over 10 or so years. The C17 would be an advancement a bit like the C130 was back in the 1960's for NZ. Everyone takes the C130 for granted and similarly the C17 would be taken for granted within a few years etc.
AD has pointed out what we all know in that the NZDF has gotten "fatter" (eg LAVIII's replacing M113's, NH90's to replace UH1's, Seasprites replacing Wasps, bigger MB army trucks than the old Bedfords or whatever they were etc).
NZ is "at the end of the line" and we all know we have committments to the Pacific, Australia, SE Asia and the Middle East currently. The C17 has a 75,000kg carrying payload to 2400nm or 45,000kg payload to 4000nm
http://www.boeing.com/defense-space/military/c17/docs/C-17_overview.pdf It's around 3300nm from NZ to Darwin thus could take 2 fully laden LAVIII's plus have enough room for 5,000kg of support equipment and troops.
Contrast this to the A400 which only has a 20,000kg payload to 3450nm
http://www.airbusmilitary.com/specifications.html which would carry only one LAVIII to Darwin but no support equipment and very little personel. (All of a sudden an A400 starts to sound like a C130, in a LAVIII context). BTW a NZLAVIII weighs around 20,000kg according to the NZ Army
http://www.army.mil.nz/our-army/equipment/nzlav/default.htm and for those that don't know, Darwin is a major staging and transitting point for the NZDF.
With air-to-air refuelling from the RAAF's new Airbus tankers (eg over NE Australia), the C17 (or A400) could certainly take a large payload further if there was some regional crises in Timor or to the north west etc.
The A400 would be a useful asset for the NZDF in 10 or so years especially for carrying lighter loads but the Govt would be kidding itself not to also invest in the C17 now/soon. This Labour Govt is unlikely though but if they did they would fill a huge capability and capacity gap for the NZDF and actually gain alot of praise (and even from the likes of us here).
The C17 could carry a decent civil defence disaster recovery team, cargo, bulldozers and trucks into the Pacific all in one hit whenever there is also cyclone damage to clean up etc.
The NZ Antarctica operation would support the C17 aquisition (as they obliquely referred to NZ needing to improve on its C130 transporter a few months ago) and would lend towards better logistics support with the USAF there.
Win-win as far as I can see.