Re: Caliber Choice for pack rifle
A Blaser R93 with professional stock would be a good candidate - you could even take several calibres with you.
Seriously it is light, Packs away but sets up to same 0 in a couple of minutes.
Expensive up front but afterwards you really only need to buy the barrels of the caliber you want. You can even use the same scope as long as it is good quality, repeatable settings - just dial in different settings for differnt calibres.
Notoriously accurate out of the box, highly weather resistant
What is the old saying - "fear the guy with one rifle" ?