I remember having this same question a few years ago. I went around and looked at all the modern touring bikes. IMO modern touring bikes tend to be overbuilt. They are optimized for a 250lb dude carrying 75 lbs + of gear. That's fine if you're going to tour Patagonia or something, but for more typical mostly road touring, it's overkill. Vintage touring bikes are more optimal. Bumping up to tourist gauge +1mm is enough, for example Tange
#2 instead of
#1 , SP instead of SL, 531 'tourist' gauge, etc. Ultimately I ended up getting a custom Mercian with OS tubeset, which gave me some extra stiffness while keeping the weight comparable or even lighter than high end traditional touring bikes.
I've had vintage touring bike in the past and it was fine then. I'm sure it would be fine now. I'd probably upgrade the wheels to modern cassette hub type, preferably with OS axles. See below. And I'd use SPD pedals. Other than that, vintage touring bikes will still do the job, and be easier to pedal to the top of that mountain.
Yeah. That's a potential weak spot. Phil Wood hubs solved it in another way BITD, with those super thick axles. The stopped making the freewheel version about a year ago though.