The first thing to say is that Australia is becoming an extremely competent manufacturer of submarines, and I would commend that to Canada when it thinks about where its next submarines should come from. I really don't mean that flippantly. I think the more we could achieve in terms of commonality of design around sensors and weapons, the better that would be.
There are many people who would say that the future of navies is all going to be underwater. There's the odd joke that “There's submarines and there's targets”. I don't completely subscribe to that view, but I have to say that I think submarine capability is an essential part of a mature first-world navy.