On second glance, Mr Peters is asking MPs to "sign up to", not literally ink any deal.
National should heed Peters if it is to overcome the prejudice that exists in New Zealand First after its first experience in coalition with National from 1996 to 1998.
It is not all ancient history: 13 members of the present National caucus of 48 were part of that coalition.
That coalition was undermined by the lack of respect given to New Zealand First by National and eventually collapsed over the sale of Wellington Airport.
New Zealand First's lack of trust in National was reinforced under Don Brash's leadership.
It is understood that some of the Brash emails that fell into Mr Peters' hands canvassed a strategy of destroying New Zealand First six months after the election, though not penned by present staff or MPs.
But New Zealand First's default attitude to National is negative.
Mr Key needs to set expectations of discipline among his right wing in the same way that Helen Clark has imposed on the left wing of her caucus.
The natural instinct of both groups is to hold their noses at the centrist, populist party.
The fact that Mr Peters is giving Mr Key advice at all is a sign that he would seriously contemplate a deal.