Boulder Mtn.,
I know what you mean about carrying a big rifle in rugged country, especially at altitude. My Mark V has not been hunted for a couple of years, & with the possible excepton of a "from the truck" antelope hunt, will not see action this coming season.
As Ron said, a shorter, stiffer barrel should not affect accuracy in a negative way. And as the others have posted, a local smith can cut & recrown quickly & inexpensively.
There are many lightweight choices in the market. It really comes down to what floats your boat. The Kimbers are beautiful. They look like a miniature Model 70. You've also got rifles from Savage, Tikka, & Ruger. Your idea of a cutdown Vanguard is good also. To me, the most important attribute of a rifle used far from base camp, is absolute reliability. Then comes overall weight & acceptable accuracy. The Howa action is certainly tested & reliable, & the Vanguard is accurate,& hopefully makes the weight requirement.
Keep the scope light, a nylon sling in your day pack, & a Kifaru butt holster on your pack belt if necessary. As you already know, it just doesn't get any better than a high country hunt.
Jim