I've been reading a bunch of pages about Jeff Cooper's "Scout Rifle" concept. There's a Wikipedia page that details his final specification. I also found a site (Jeff Cooper's Commentaries) with Cooper's newsletters from the 1990s where the concept was evolving.
Basically, the specs were:
Light weight; between 6.5 and 8.5 pounds empty
Bolt action, though he said he had no objection to an autoloader
Short barrel, 16.5 to 19 inches
Powerful cartridge, .308 class or better
Bisley or Ching shooting sling
Overall length 40" or less
Forward-mounted 2x or 3x optic, or "ghost ring" or peep sights
The idea was basically for a "single rifle" that would be light, handy, and powerful enough for combat or large game. Not necessarily optimal for anything, but good enough to do the job.
The optic part took a while to figure out. Cooper was a fan of snap-shooting or wing-shooting, and his working scenario was that you'd be shooting at 50 to 100 yards max. The forward-mount optic (about where a standard AK rear sight would go) was partly because he felt you should be shooting with both eyes open and looking toward the target, and the long eye relief would make that practical.
Cooper's specifications changed over time. The interesting thing is, an AK-47 and an optic meet most of the specs. So would many leverguns.
The other thing is, a lot of the "truck guns" and "hog guns" I've seen people build meet at least the spirit of Cooper's concept. Short, light, forward sights or optic, healthy cartridge.
I haven't shot a rifle with a long-eye-relief scope yet, so I'm still dubious about the whole "both eyes open" thing. (or maybe I've been shooting "wrong" the whole time...) I thought I saw a 1.5 Burris pistol scope in one of the boxes last time I was cleaning... I might whittle out something to mount it on an AK and see how it works out.