Millar has suggested that a tournament, held every two years, between rugby's top test nations would cement a regular fixture programme into the hectic schedule.
"It would enable us to fulfil the needs of unions to produce the necessary finances," he said.
"There are a lot of test matches now compared to what there used to be. But there is a requirement for income. Players have to be paid and rugby is a very expensive game to play with all the back-up staff.
"We have to look maybe at some other formula rather than just have the Southern Hemisphere countries coming here in the autumn and playing a few matches and the Northern Hemisphere sides going to the Southern Hemisphere in May and June.
"It would solve many things such as concern over player welfare and number of matches. It would create more relevant games and be a more effective way of increasing revenues.
"But people will have to compromise and change to create these things.
"There is no need to tweak the Six Nations or Tri-Nations to any degree, but we have to look at the autumn internationals and summer tours so there are enough games that generate sufficient revenues," he told The New Zealand Herald.