Canada won't get a carrier, period. For starters, naval aviation was 25% of the total naval budget, and the navy fought tooth and claw to keep Bonaventure as long as she did. Secondly, she was at her prime just after her last refit (and a huge pile of money had ben pured into her), and they still scrapped her.
The problem wasn't with Trudeau.. well, him too. But it started with Pearson and Hellyer. The navy fought unification tooth and claw, and lost many good senior officers over it (Brock and Landymore being the big ones), and once it happened there was really no one left with much of a say in the navy on how it should be run. Really guys, they made the naval uniform green for God's sake.
You are correct on all front here, which is why I set this up for the early 1970s. The loss of so many Naval officers post-unification damn near destroyed the Maritime Command - for a while, they only had the Iroquois and Oberon class boats, which most of the others were laid up, and even by then the fleet was obsolete. I can see the 1968 revolts by the Navy spreading to the Air Force, which still remembered the loss of the Arrow. Get that bad and you'd need whoever Pearson's successor is to start making things better. Trudeau wouldn't do that of course, so by the time Stanfield rises to power in 1972, he's got a massive mess on his hands and Canada's ability to work within NATO would be seriously threatened. Nixon would almost force him to do something about that, especially as the US military reloads and rethinks its messes and problems from Vietnam.
Hence, by 1972, you have a Canadian Forces that is falling to pieces, a PM who wants to make an impact, an opposition party that wants both jobs and to show to the Canadian public their opposition to communism. A cheap British carrier that is about to be scrapped that needs a major refit - that a Canadian yard can do - makes a statement. One can imagine how much flagwaving the Canadian Forces can do when they get to show off their beautiful new 50,000-ton carrier, which if they did it right has American or British weapons systems but for all intents and purposes is a Canadian vessel.