Black Caps are susceptible to such freelance deals because NZC cannot afford to pay them the same retainers as peers operating under larger economies of scale in India, Australia and England.
"My decision was a product of the circumstances," McClenaghan said.
"I'm currently on the fringe of selection for the [New Zealand] one-day [international] and T20 sides, and this gives me greater financial benefits and a lot more time on the park playing the game I love."
Despite signing the original contract by the cut-off date of June 28 for an August 1 start, McClenaghan said his position had changed in the last 10 days, notably through a deal with Durban in South Africa's Global League. That tournament clashes with the New Zealand domestic summer.
"New Zealand Cricket have been outstanding in understanding my position and potentially allowing me to be available domestically or internationally when I don't have tournaments on.
"But I accept the likelihood of me playing for New Zealand again is slim."
McClenaghan leaves the international limited overs game with world-class numbers. He played 48 ODIs for 82 wickets at an average of 28.2, strike rate of 28.4 and economy rate of 5.94. From his 28 T20Is he took 30 wickets at an average of 25.26, strike rate of 19.6 and economy rate of 7.7.
"Whether this [new move] is for six months or four years, hopefully I can come back at some point to offer my knowledge, or preferably skills, to help New Zealand win a World Cup or other pinnacle events."
Shane Bond is a former Black Cap who saw too little time back in the national side after signing with the now defunct Indian Cricket League a decade ago.
He has mentored McClenaghan as a bowling coach in the New Zealand environment, and latterly with the Mumbai Indians in the Indian Premier League.
Bond says McClenaghan has made a logical move as the cricket market further adapts to its audience.
"It's getting to a point with so many tournaments around the world that there are options for players.
"This is Mitch's opportunity to go around the world and make a fair bit of tin, so good on him.
"It's still a difficult decision to opt out of a national contract, but if you're a player lower down the contract list, the comparison with potential earnings can be significant."
Bond said timing's everything because a good run of form in ODIs or T20Is can mean players stand to make "a decent hunk of money in the space of a year".
"We're seeing that in rugby where players get sabbaticals to go to Japan. The World Cup's two years away so Mitch might go away, do well for a year, and assess if he wants to keep doing it. That might then pose an issue for the selectors, but that's the cricketing world we live in now," Bond said.
"He's a very good T20 bowler, a game changer who's fearless and prepared to mix it up. He has the perfect chance to get stuck in. Who can blame him?"