NZRPA chief executive Rob Nichol applauded Key's suggestion and explained that benefit games were being considered, but it was necessary to first establish the trust to ensure any ideas were executed properly.
"In regards to the Prime Minister's comments, I thought they were really sensible," said Nichol. "The memorial match, or the concept of playing a game or a couple of games, to support both Jonah's legacy and celebrate what he achieved and to support the upbringing and education of the kids is a great idea and it has been thought about right from day one.
"There have been a number of offers to stage games and, in due course, they'll all be considered. There are a number of parties to think about from World Rugby to New Zealand Rugby to family and different people.
"But it's important for people to understand that it's all very well to go out and do cool initiatives to raise funds but it's actually quite important to have a sensible structure to be able to apply those funds to.
"Part of the idea of forming the trust is actually to provide a trust that can transfer that in a really meaningful way. So it was actually about establishing that and then you can give context to some of the ideas and assess them in terms of those strategies."
The idea of staging benefit games both in New Zealand and abroad has attracted a lot of public support on social media.
Lomu has a huge profile in the UK and Europe and the benefit cause would be sure to attract the interest and support of international players past and present.
When contacted for comment on the idea, New Zealand Rugby chief executive Steve Tew said in a statement: "This is obviously an incredibly sad situation. From a rugby perspective, we acknowledge that we will want to find an appropriate and fitting way to recognise Jonah's contribution to the game, just as we have recognised other rugby greats such as Jock Hobbs, Sir Colin Meads and Sir Brian Lochore.
"That may or may not include helping the trust but no decision has been made to donate directly at this stage."