Ruebee - thank you.

So let me get this straight:

So a waypoint's co-ordinates were changed but the waypoint's name remained the same?

There was no NOTAM or crew notification of the change in co-ordinates?

There was a company/crew briefing held days (weeks?) earlier based on the route with the previous co-ordinates?

The briefing based on the previous co-ordinates could have been confirmed had 1. Collins diary pages not mysteriously disappeared from the accident site, 2. The break in at Collins house which saw his atlas stolen but nothing of value went missing. This atlas could have also helped proved which route was briefed. 3. The company had not shredded documents which could have helped prove which route was briefed. 4. The FO's house was also broken into, nothing of value was stolen but documents which could have helped prove which route was briefed were removed.

Collins descended below MSA based on achieving visual reference with ground or water from a position derived from the INS but did not cross reference this position with a ground based navigation aid that didn't provide distance information unless it was loaded into the INS as a waypoint?

Collins subsequently lost visual reference but didn't realise until it was too late? Collins could have been subject to visual illusions that the human factors crowd hadn't had a lot of understanding of or had much data on?

Assuming that all of the above is correct, had Collins made a missed approach based on the route he thought he was on, would the aircraft have been safe?

The name is Porter ;

Collins descended below MSA based on achieving visual reference with ground or water .................................................NO, Collins was in VMC when he descended as per the Air NZ SOPs.

Collins subsequently lost visual reference ..............................................another assumption with no evidence to support it.

Assuming that all of the above is correct, had Collins made a missed approach based on the route he thought he was on, would the aircraft have been safe?

A ambiguous question and based on your own incorrect assumptions, answering it would require too much speculation. What is indisputable and a fact, the final waypoint was changed the night before the flight by the Air New Zealand navigation department and they failed to advise Jim Collins and his crew.