Journeyman, we need to be ready to fight the next war, not the last one. I'm not sure if you've noticed, but Mr. Putin has been getting a bit big for his britches off late. He has also been making noise about the arctic, (as have the Chinese). As much as I respect the Canadian Army, they have next to no use when it comes to maintaining our claims in the resource rich Arctic Ocean. The RCN could do it, if we bought them nuclear subs (which is not likely). Like it or not, the only service that can project a sustained presence in the Arctic is the RCAF. Like it or not, that is where the next cold war is going to be. We could leave it to the Americans to defend the arctic; I'm sure they'd been most happy to, given that possession is 9/10ths of the law. This would, however, amount to relinquishing our sovereignty in the region. Long story short; if we want to maintain our own territorial sovereignty, we are going to have to do it ourselves, and we will need the F-18s, (or F-35s or Typhoons.....) to do it.
Any time we are going to need CAS we are going to be operating as part of a coalition. We can get CAS from our allies. So, if it comes down to choosing which capability to prioritize, (which in the current fiscal environment it does), it's in our best interest to keep our fighters, and to use them for NORAD.
As for who should own CAS, (in a hypothetical world where we could afford dedicated CAS assets), it should be organic to the ground forces and operated by fully trained aviators. Making it organic to the ground forces allows the supported commander to put assests where he needs them when he needs them. Having it operated by aviators ensures that it doesn't become a stick in the spokes of the overall air effort.