My suggestion of who should be the next leader of the National Party is...
Chris Hipkins.
Up side:
* He's a fundamentally decent person.
* He could bring with him a competent economic manager (Barbara Edmonds), a talent which the current Nat leadership sorely lack.
* He's proven that he's able to work with solid Labourites such as Kieran McNulty.
Down side:
... I can't think of any yet.