Mr Day said the restructure was a strengthening of aviation health and safety and operational requirements.
"We want to have the best structure we can have, and we need people in roles that can do these things.
"We've got a lot of experience - it just needs more concentration, breaking down into more specific roles."
Mr Day would not comment on Mr Greenberg's role as helicopter crewman if he was not successful in an application.
Mr Greenberg, a former New Yorker, became involved with Wellington's rescue helicopter from 1991, starting as a volunteer.
He has been involved in more than 3500 rescues and received a Search and Rescue Award for his involvement in the recovery of an Air Force crewman from a crashed Iroquois helicopter on Anzac Day 2011.