I can't answer that question as I don't have the technical expertise to even begin formulating an answer.
But....always a 'but' with me....answer this question - who and where is Canada most likely to fight?
Is the 'where' the following places:
1) Over northern Canada/Alaska
2) Within somewhere in Europe
3) ?
Is the 'who' the following:
A) Russia
B) ?
Can the Gripen address #2 first and then #1? The 65 F35's primary role will be to address #1
Can the Gripen handle the majority of #A type jets that it could face?
Again, I'm not saying that I'm advocating for a F35/Gripen fleet, I'm raising questions about it. Personally, for me, I'd like to see 102 F35s with the RCAF roundel on them - 5 full squadrons of them proper training/spare numbers purchased.
If you have a solid network of ground, air and space-based surveillance to identify any aircraft (or more likely missiles) entering Canadian airspace do you really need your stealth platform for that?
I'd argue that the F-35 is best suited for our expeditionary ops where the stealth will be required to either penetrate AD coverage or engage enemy fighters. For NA defence you're not going to see SU-57's flying over Vancouver. At worst you're going to see Russian (Chinese?) fighters escorting non-stealthy, long range bombers that are going to launch their cruise missiles from as far away as possible to ensure their own survival...or you'll be engaging sub-launched cruise missiles on their way to their targets.
Personally I think that it makes sense for Canada to go for an all F-35 fleet for the sake of commonality and the ability to use ALL of our aircraft in ANY potential role. I also think that Canada engaging in combat against Russia/China in Europe/Asia is much more likely than either of those countries launching a large-scale missile attack against North America as that would risk being perceived by the Americans as a pre-emptive nuclear first strike and elicit a US nuclear response.
IF Canada were to look at a mixed fighter fleet my preference would be for F-35's/F-15EX's simply due to the EX's range, payload and interoperability with the US's EX fleet which is doing the same NORAD role as ours would be doing. However, buying EX's instead of F-35's would make no political sense (they are both American) and wouldn't make any economic sense (EX is similar or higher up front cost and you lose the benefits of a common fleet).
IF Canada goes with the Gripen it would be a purely political decision. We would lose the benefits of a common fleet and would certainly antagonize the US with the decision. We would probably get some industrial benefits from domestic assembly but would it be enough to counter any potential loses from our current F-35 component contributions? It
might breath some new life into the proposed Next-Gen Gripen development if it expanded the user base enough but certainly no guarantees so we would likely end up with a dead-end airframe that will have to be replace with something completely new in 30 years.
Personal opinion? A mixed fleet of say 66 x F-35's and 66 x Gripens (you'd need those numbers at least I think to cover both an F-35 expeditionary wartime mission and maintain sufficient aircraft for defence of North America) would stretch pilot training, technical support for the split fleet and overall cost to the CAF, but I doubt would really have a huge impact on our overall combat capability. 66 x F-35's should be able to support a deployed squadron for overseas operations (I doubt we'd ever send more than that regardless of our fleet mix) and 66 x non-stealth Gripens could handle the NORAD mission in the unlikely event of a large scale attack on North America.
Still...would be a big time waste of money and resources to my mind. Stick with an all F-35 fleet.