All of this speculation about acquiring C-17s or A-400s isn't going to happen, the current government chose to upgrade their 5 C-130s instead. The completion date for the upgrade is around 2010, with the aircraft expected to last another 10-15 years. Therefore, the C-130s should last until 2020-2025. Any new transport aircraft won't show up on the defence forces long term development plan until 2015 at the earliest.
The MRV will be commissioned early next year. It can move 250 troops, its equipment, plus 4 Hueys and supply the force for a month. A typical company's equipment would be 16 LAVs, 14 LOVs, 7 Unimogs, 2 ambulances, 2 flat bed trucks, 7 LOV trailers, 2 rough terrain forklifts, and 4-four wheel drive vehicles, in addition to up to 33 containers.
It appears the government wishes the MRV to do patrol duties for 100 days during the summer months in the southern ocean. Considering the ship can sustain a top speed of 19 knots, if the ship were 1900 nautical miles away it would take 100 hours (a bit more than 4 days) to sail back to New Zealand to load this company. And from what I have seen this week, I doubt whether the army would be ready to load in 4 days.
More than likely it will take the ship twice as long to reach East Timor. But it appears the MRV can get all of the force and its equipment there with one trip. Yes, C-130s and Boeing 757s can get the troops and some equipment there quicker.
Yes, acquiring one or two C-17s would upgrade New Zealand's airlift capabilities considerably. Since the current government chose to eliminate its air combat force to save on operational expenses for fighters that were never used, maybe the current government could spend those funds on C-17s that would be used. Highly unlikely.
Frankly, the MRV would be nice to have presently, as would the one of the Boeing 757 and one of the C-130s, which are being upgraded currently.
As far as the replacement for the P-3 Orions, the P-3 line is closed. If the Americans choose the new up to date P-3 Orion over the P-8, a Boeing 737 make, New Zealand could purchase either. Like the C-130s, many worldwide are being upgraded to last longer.