He is a former national 125cc champion and last year raced in the MX2 category but the future for him now is on the 450cc bike.
"We have brought Ethan in because, although Billy is from overseas [Scotland], the team's goal is to support and develop the Kiwis," said manager Josh Coppins, who has just returned from managing Team New Zealand at the Motocross of Nations in Germany.
"I think Ethan has been riding the MX1 bike really well."
In addition to Columb, Vaughan and Martens, BikesportNZ.com rider Logan Blackburn, of Te Puke, will be on board an Altherm JCR Yamaha YZ125.
"We really wanted to cover all the classes. This is part of our programme to develop riders," Coppins said.
"At the end of November the riders will all gather down here [at the team training facility in Motueka] for testing and training, but this Taupo event is the team's first big shake-down.
"Our goal is to win all three classes and we have the riders to do that.
"We will have two main team riders, Scotty Columb and Billy MacKenzie, and support riders too - Ethan Martens, Cameron Vaughan and Logan Blackburn. It is a tiered system and we still have Hamilton's Josiah Natzke and Otago's Courtney Duncan to come into the mix."