Good scenario, but all these Commonwealth realms switching to seemingly similar semi-presidential systems doesn't make much sense to me considering the strong parliamentary tradition they all share.I mentioned in my original post that the Australian election led to a Labour landslide for Gough Whitlam. He eventually took virtually the same path as Trudeau--a referendum with overwhelming support from nearly every political party, and he was sworn in as Australia's first president. Almost the entire Commonwealth followed this path because the revelation made the Windsors universally distrusted.
Full disclosure, I'm not very knowledgeable on non-contemporary AU/NZ politics so I'll have to do a bit more reading. I'm thinking either Keith Holyoake becomes the first President or Norman Kirk defeats him at an election and he becomes the first President.