Yeah I'm rather excited about the Sig 556 XI supposedly coming later this year - interchangeable/ambidextrous controls and an easily replacable barrel (CAN YOU SAY QUICK SWAP SBR?)
That said I do recall the article you mention - here is a link to several bits of information from Arizona Game & Fish regarding the Jaguars in Arizona.
So they are so rare that its not really a risk that I worry about - I'm much more worried about the flow of drug dealers and violence north - and meth makers and pot farmers in the national forests - especially when I'm deep in the sticks. I have pictures of different things I've seen on the border stretching back a few years, everything from a truck load handoff, signs from the border patrol telling people to avoid certain areas, garbage, bloody knives etc. A few years ago a buddy and I were down south and had some "guys in a truck" pop off shots in our direction trying to scare us off. I figured they were drug runners but we were told by the authorities it "probably wasn't" :rollseyes.
Anyway - I love my 45-70 but bought it because I love it but if I had to give a 'reason' mainly for camping in Idaho & Montana with friends & family. Running modern ammo its far too overpowered for most anything south of Grizzly, Moose & Caribou. Even Elk it seems a mite heavy. Mountain Lion (which I apparently smell like kitty snacks to them) can be handled with a loud noise and rocks most of the time but when their hungry even a 38spcl will take care of them. A Jaguar is big but they are fairly thin skinned and don't worry me, and as I've already mentioned, not really an issue. Besides even in South America they tend not to be serious threats to humans. I'm working on a project to extend the normal range of the 30-30 with better ammo & sights, as well as making it more compact. If I can get to consistent 350-400 yard shots with it I will probably retire all of the others unless the terrain changes. But time will tell.
I wonder if thats why many of us have AR's & AK's for truck guns is because of other people, not so much the natural predators out there. Just a thought.
Besides whats camp without a little shooting if its safe and in an acceptable area?