I don’t mind that Shane Reti is the interim leader. The main reason being, if you are going to do this, try and do it properly. Far better to make a solid, well considered decision over a mad cap heat of the moment one. 
Whether Reti held the job for a while will matter not in the fullness of time. 
As for poor old Judith Collins, her demise will be quickly forgotten as well. We don’t spend a lot of time talking about the David Shearer years, the David Cunliffe years, the Andrew Little years, or the Bill English years. Not that most of them even had years to talk about, sometimes just months. 
The point is once you're gone, you're a feather duster. 
The real issue for National at the moment, is not as much the next leader, it's whether they gather in unison behind them. At one point there were plenty of people who thought Collins was right for the job, that’s how she got it. 
But the ensuing bitching, backstabbing, leaking, and general self-indulgence would have done anyone in. That is their major problem. If they cannot tidy up their discipline, you can elect anyone you want, it won't make a lot of difference. 
Yes, a leader can unite, a leader can spark the public's imagination, and from that comes a sort of fait accompli within something like a caucus. But the fundamentals of basic professionalism have to be there from the start. 
So, Mark Mitchell or Christopher Luxon?  Either is good or potentially good. 
Luxon has not shown himself to the wider world. So, he might be brilliant, or he might be a David Shearer type. Luxon ran a company, Shearer helped the third world. Both are affable, both looked like a prospect.  What you did and your back story is but a small part of the ingredients required to win in politics, though. 
A lot of Luxon is based on the idea he's the next John Key. He looked unlikely until he got Teflon. Even Collins looked kind of fun with the old crusher persona until it vanished with the pressure of leadership. 
Simon Bridges was the same. Never forget, lots of people liked him until they didn’t. There is a very real tangible step to be made between looking good and actually being successful. 
Mitchell? We know him well. To be blunt, we got him on the Wednesday slot because we thought he would end up, well, where he might be about to end up. Is he too nice though? 
Are either of these blokes just contenders because that’s all there is? Is Luxon a genius? Or just another bloke who looks okay, until we find out he's picked the wrong profession? So, the race is on. 
But here's the simple truth, National have made a spectacular mess of this. You have to earn support no matter who your leader is. If they can't see this as a circuit breaker, then ACT deserves to be the opposition.