Now the South African-born left-arm strike bowler is finally eligible, his inclusion in the national team should be a formality.
The 26-year-old has spent the past four summers playing for Otago and has built up an impressive resume while waiting to satisfy the ICC's eligibility criteria. In the last two seasons he has taken close to 100 first-class wickets with a combination of reverse swing and some good, aggressive fast bowling.
He has not been as successful with the white ball and, like everyone, has some limitations. He struggles to hit the seam consistently, his pace varies quite notably and there are some question marks about his mental toughness. But he is still honing his craft and Cumming, who retired at the end of the season with more runs and centuries for Otago than anyone else, believes Wagner is ready to make the step up to international cricket.
"From a batting point of view, the selectors are willing to pick guys who have performed for part of the year. Well, Neil has backed up with four years of strong performances," Cumming said.
"He deserves an opportunity."
As Cumming sees it, Wagner's skill set is well-suited to the conditions the Black Caps are likely to find in the Caribbean.
"Neil is not a big seamer of the ball, but what he is the most skilled at in New Zealand is reverse swing. That is the reason he got five wickets in six balls [in Queenstown two seasons ago].
"The pitches over there are barren and there is not a lot of grass on them. The ball roughs up and it doesn't seam a lot but it does reverse swing, and I don't think we've had a real great exponent of reverse swing for quite a while.
"He has picked up half his wickets for Otago doing that and he does it earlier than any other bowler I've seen do it. It just adds another weapon to the New Zealand attack."
His ability to get the old ball to bend back into the right-hander should put him ahead of the likes of fellow left-armers Trent Boult or Andy McKay.
"McKay is probably quicker through the air but I think Wagner adds more variation. But if you were looking at conditions in England, where there is genuine swing and seam, then someone like Boult would come into play.
"But I think New Zealand cricket is lucky because they have bowlers to pick from who will suit the conditions."
A polite and likeable chap off the field, Wagner changes character when he is running into bowl. His emotions get the better of him from time to time and he is prone to the odd act of petulance. Whether it is just kicking the turf or getting in pointless conversations about the merit of a particular shot, he certainly takes it further than a rueful glance.
"Emotionally, without a doubt, he has his ups and downs. That is probably one of the things he has worked on harder this year under [Otago coach] Vaughn Johnson.
"I think Vaughn was really hard on him about that and I think we saw some strides forward. But controlling himself is something he needs to keep getting better at," Cumming said.
"He is combative and that is one of the reasons he has been successful. He does like to get into the fight and sometimes a lot of the kicking the turf is actually because he is frustrated with himself. We just can't understand it because sometimes it is in [Afrikaans].""When he gets his nostrils flaring he can certainly bowl quick and he is aggressive. And it is not skiddy quick. It is at-you quick."
