To my knowledge, replacing the Monarch is far easier than most probably believe.
Most people like Queen Elizabeth II but don't like the next few royals. And when the monarch dies, Parliament decides who will succeed. I think it would be possible to have Parliament to never pass legislation to confirm a new Monarch or maybe, I'm not sure about this, to vest itself and the GG with the authority of the crown. Though this has to be vetted and OK with those who rely on the institution of the Crown.
It'll be interesting for sure. It'll be the first time the Canadian Parliament will be choosing its own head of state after the repatriation of the Constitution.