Not solely for Barrett, either. Brodie Retallick, the world's leading second-rower, and Crusaders captain Sam Whitelock are among others believed to be mulling this option, should it come to fruition.
"That concept of Japan 2020 comes up in a number of conversations," New Zealand Rugby head of professional rugby Chris Lendrum confirmed to the Weekend Herald. "It's not necessarily a real prospect for everybody."
Japan is yet to finalise its season structure beyond next year but the World Cup, which kicks off in September in Tokyo, has forced the 2019-20 domestic campaign to be pushed back to January the following year.
Likewise, New Zealand moved its provincial season when staging the 2011 World Cup.
Japanese rugby tends to move at its own pace but if discussions progress towards the two-seasons-in-one, this could be enough to sway Barrett and company.
Ultimately, Japan would open the door to the best of both worlds.
Barrett would have the freedom to commit to a fresh long-term deal with the Hurricanes and NZR but first take leave - as Dan Carter and Richie McCaw previously enjoyed - before returning for another crack at the All Blacks and 2023 World Cup.
"Generally what we understand is they are looking to run two Top League seasons during 2020 but that's not confirmed," Lendrum said. "If they do it seems like there is an opportunity for players to go there and play those two seasons effectively in the space of one New Zealand calendar year.
"From a salary and welfare perspective that has obvious attraction for players who potentially have had long Super or international careers and are looking to refuel body, mind and wallet for maybe another few years."
The Japanese Top League has already lured All Blacks Carter, Israel Dagg, Matt Todd, Richard Kahui, Andy Ellis, Augustine Pulu and a host of other internationals. Wayne Smith (Kobe) and Robbie Deans (Panasonic) are among Kiwi coaches there.
The Top League's high tempo style is considered much easier on the body from a physicality perspective, especially when compared to the relentlessly long and brutal European game.
Spending up to six weeks in Japan during the World Cup will also allow All Blacks to adjust and adopt Japanese culture prior to a potential move there.
And while Japanese salaries generally don't match those in France, there may be potential to stitch together healthy commercial agreements.
So often outbid in the constantly challenging player market, NZR is always attempting to find creative solutions to counter this on-going issue.
"From a New Zealand Rugby perspective, plan A is to always have players stay and play in our competitions all year round and be available for the All Blacks," said Lendrum.
"If we had to push for a plan B because plan A wasn't available due to circumstances of a particular player, then it is true that two seasons in one Japanese prospect is more attractive for us to work with than seeing somebody head out the door to France or England."
Of course, any player who leaves the All Blacks risks others grabbing their chance in the jersey. In Barrett's case that would be Richie Mo'unga.
"People are still really motivated to seize an opportunity to play for the All Blacks if it is apparent. Some players are waiting to see what other players do."
Given the expected, now common, World Cup exodus, coupled with the potential short-term loss of other senior All Blacks to Japan, fears may grow for how Super Rugby will look in 2020.
"We're always worried in one sense about making Super Rugby as strong as possible and ensuring it has as much of our top talent as possible. It is true there will be some players who won't be there in 2020 who were planning to leave anyway,'' said Lendrum.
"This other Japanese concept, it's to be seen. It may have an impact but I don't expect it to be significant. I'm confident Super Rugby in 2020 will still be a highly entertaining proposition."
