I think you are seriously underestimating the cost of ownership difference between the SH and the F35, certainly when we talk about those countries already operating the Hornet.
Besides the training and implementation which will be substantially cheaper for both ground and aircrews, there is also the fact that all of the weapons in stock remain usable, AAR infrastructure that needs no changes, much of the infrastructure that needs little change.etc... .
Also it would put the 1 vs 2 engines debate to rest and the avionics on the latest SH are at least equal to the F35 with the added benefit of having buddy to buddy refuelling option and the Growler upgrade.
Operating 2 types does make sense starting from a certain number of planes.
they basically can put one type on each base and build its infrastructure around it while keeping an operational centre for the other type on the other base(s).
Arctic patrols with SH aided by the A310's makes a hell of a lot more sense than doing it with the F35.
Also landing on emergency airfields or suitable roads, frozen rivers, etc... will be much more doable with the SH wich basically has the NAVY specced gear.
Also the SH has a lot of growth left in it, the engines are now 22,000lbs but can easily deal with 20%more power.
It can also load up to 8T of weapons and with the new stealthy weapon pod it has the added benefit (contrary to the f35) that it can jettison superfluous loads (tanks, weapon pods, bombs) when it needs to so it can bravely but quickly and light leave the battle-scene heroically to fight another day.
If it was up to me I would go all SH, but the Canadians seem to be holding on to the F35 jobs program no matter what.
This is basically the only way they can keep their position in the F35 program while at the same time keep a credible and sizeable air force.
Besides all that,
It seems that the US Navy is still not giving up on the idea of scrapping the F35C altogether.
Averting the Navy's Tactical Aircraft Crisis | U.S. Naval Institute