You point to one of the very positive things about this Continental tire: thinner sidewalls than average. There's a lot of flex. But the tread also has an almost insanely high wear rating of 540; in 30K miles on my Z I only lost an average 2-3mm apiece. And the tread, 275 mm, will NOT "tuck under" -- that's a 10.5" wide contact patch and you've got a comparatively light CX-5 sitting on top of that!
I'm saying the OEM 19" rims are do-able and safe at 7.5" wide, for a 10.5" tire. Would I do that myself? Hmm ... I'd defer to the judgement of someone at tirerack.com, if I thought I could live with the look. However -- I would risk it if I was spending 2K on rims I couldn't barely tell apart from the OEMs.
I have issues with your decreeing things safe/not safe, since we're really only talking about the tire bead staying fully engaged under all prospective driving conditions. However, on the aesthetics, we might be closer. It may be that a narrow rim just looks fugly, like anything you see with a massive negative camber.
My FWD GT Tech on 19" Toyos has almost no noticeable understeer. AWD should be significantly less. Staggering, on a car like the CX-5, is to create a unique profile, ie, "looks", and you might go with a 17" rim front (with high profile tire) and our favorite 19" 275/35s in back. (Or go even crazier with 22s.) The point is that you're not autocrossing a 182 hp car; you're cruising with it.
I was 3/4ths serious when I asked Rick if he was going to do a blower, because as perky as this CUV is, it's not a Gojiro-slayer. (Yes, that was the other direction I could have gone when I said goodbye to my Z, and a Nissan GT-R was achievable, if not terribly practical. Now I drive a very enjoyable little CX-5 that I can't pick out of a parking lot full of Ford Focuses, Hyundai Santa Fes, Kia Sorrentos, Buicks... well, at least I know it's not a CR-V.

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