Experienced campaigner Dwayne Sweeney comes into the midfield, alongside former All Blacks Sevens player Sam Vaka.
Sweeney has signed for Waikato in 2017 and is set to add to his 77 provincial caps earned for the Mooloos. Bay of Plenty lock Keepa Mewett and halfback Richard Judd join Steamers prop Aidan Ross in the squad.
Super Rugby experience will be injected into the forward pack with Andrew Makalio, Oliver Jager, James Tucker, Mitch Dunshea and Lachlan Boshier set to bring more strength up front.
"We have put in a lot of planning to get to this point and are looking forward to spending time as a group and see it all come together," McMillan said.
"This is a huge occasion for our players and management, and I know everyone is eager to get things under way and create history."
The squad assembles today and will travel by bus to Whangarei on Sunday. They will be welcomed to the city with a powhiri on Monday and are set to get out into the community later in the week with some school visits.
Players unavailable because of Super Rugby commitments are Hame Haiva (Blues), Quentin Strange (Crusaders), Mitch Brown (Chiefs), Heiden Bedwell Curtis (Chiefs), Jonathan Taumateine (Chiefs) and Johnny Fa'auli (Chiefs).
New Zealand Provincial Barbarians v British and Irish Lions
Forwards:
Aidan Ross (Bay of Plenty), Tolu Fahamokioa (Wellington), Sam Anderson-Heather (Otago), Andrew Makalio (Tasman), Marcel Renata (Auckland), Oliver Jager (Canterbury), Keepa Mewett (Bay of Plenty), Joshua Goodhue (Northland), James Tucker (Waikato), Mitchell Dunshea (Canterbury), Lachlan Boshier (Taranaki), Matthew Matich (Northland), Peter Rowe (Whanganui)
Backs:
Jack Stratton (Canterbury), Richard Judd (Bay of Plenty), Bryn Gatland (North Harbour), Dwayne Sweeney (Waikato), Kaveinga Finau (Inga) (Canterbury), Jonah Lowe (Hawke's Bay), Sevuloni Reece (Waikato), Sam Vaka (Counties Manukau), Luteru Laulala (Counties Manukau), Junior Ngaluafe (Southland)