The idea of Winston Peters as Secretary-General of the Pacific Forum is a very good one, even though the reasons are not politically correct.
First of all, you need a SG with a strong governance back ground. That almost rules out anyone not from Australia or NZ.
Secondly you need someone who will not be resented as the colonials trying to tell Pacific states what to do. This is why there was significant resistance to Australian Greg Urwin. As Peters is part-Maori, this makes him far more palatable.
Thirdly I hear from numerous sources that Peters is in fact doing a pretty good job with the Pacific, and is quite committed to it.
Fourthly a former NZ Foreign Minister would bring prestige to the role.
Finally it would provide a diginfied exit from NZ Politics for Peters into a significant role, not just a diplomatic posting which would be seen a final bauble.