I believe Canada really does need to be on the cutting edge. Having spent many hours over Arctic rock and cold water in a 20-year-old airplane that was prone to engine failures and lousy in a 14kt crosswind, I'm kind of biased, I guess. The CF-18 is an excellent frame - but aging. That being said, if the fighter is intended for Arctic sovereignty, it's my opinion the F-35 isn't the right tool for the job.
First off, it needs too much ground support. Infrastructure is the first thing to go should shyte happen. My preference would be something akin to robust Russian fighters - where you can dig it out of a snowbank, plug in an APU and go skyward.
Second, with the size of our projected fleet, in a defense role, I would prefer something that presents the radar image of a much larger incoming fleet to any potential threat with the ability to detect.
Third, a back-up engine would be a major plus. Experience taught me that even one feathered propeller and three spinning ones is un-nerving as hell when you're a long way from home. I never did jets, but I do know zoomies like getting home too.
Damn! It's a pretty airplane, though....