Sunday's sold-out Pacific Championships final has served as another reminder of Test football's potential, with Tonga supporters taking over CommBank Stadium.
Samoa did not feature in this year's tournament while on a historic two-Test tour of England, but will return for the 2025 event against Tonga and New Zealand.
The Tonga-Samoa clash already looms as one of the biggest blockbusters of next season, with a thought it could attract up to 50,000 fans in a big enough stadium.
But Leniu believes more is possible.
He missed this year's England tour through personal reasons, but was part of the Samoa side that reached the 2022 World Cup final.
Spencer Leniu performs a Samoan war dance before the 2022 World Cup final against Australia. (Tim Goode/AAP PHOTOS)
The prop has also openly spoken about how Jason Taumalolo's switch to Tonga in 2017 inspired his own decision to prioritise Samoa.
And after watching Tonga reach this year's Pacific Championships final, he believes the time is right to strike for the two Pacific nations.
"Hopefully they can do an Origin series with us and Tonga," the Sydney Roosters front-rower said.
"It's probably the biggest Pacific Island rivalry between us and Tonga. It's unbelievable to see what they did this year making it to the grand final.
"I reckon Tonga and Samoa has to be like an Origin series. It would be unbelievable. Probably (play) one in New Zealand and then one or two in Sydney or Brisbane."
Leniu's comments come after officials from New Zealand expansion bids argued last week that a north-and-south Island Origin series could be part of the future of the NRL.
While that could be played at same time as the NSW-Queensland Origin series, a Samoa-Tonga series would not be as easy to schedule.
Tonga fans go wild after scoring a try against Australia in Sydney. (Mark Evans/AAP PHOTOS)
Eligibility rules allow players to represent both their state and Pacific nation of heritage, with 13 of this year's Origin players having also represented Samoa or Tonga in the past four years.
An end-of-year three-match series between Samoa and Tonga would then be a better fit, but could impede on the current success of the Pacific Championships.
The door could potentially be open for more flexibility in the representative calendar when the NRL expands to 20 teams, with the possibility of a shorter regular season.
"I don't care when, I just want it to happen. There is no bigger rivalry than us and Tonga in the Pacific," Leniu said.
"They hate us and we hate them so it'll be a good game. There's so much respect for them and what they've able to achieve for their small nation.
"Us two countries going about it on the biggest stage would be good for both nations.
"You could double (Sunday's crowd of 28,728). It was majority Tongan fans, but we'd have the same number of Samoan fans there so it's be blue and red."
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