Great thread start! I like things to be quantifiable and measurable so that they become attainable. So... How about some bench-marks

Basic capabilities:

Climbing - trees and rocks
Swiming
Walking
Running
Lifting
Carrying
Fighting

Basic Strength bench marks

Strong enough to lift self with arms atleast 10 times (this should cover climbing) - chin-ups and push-ups

Strong enough to lift and carry whatever you consider a 3 day BOB for 3 days on the move quickly

Ability to run 5 miles

Ability to swim 3 miles

Ability to hold off proportional attacks in hand-2-hand combat. This isn't the 90# lightweight fighting the 250# line-backer but the 90#'er against similarly fit 90#'er. Other fight situations need to be met with tools such as stealth, chemicals, edged weapons or firearms (probably in that order).

This is not a very high mark but it will be a decent start on bing fit enough to handle most situations.

If you are already severly obese or have cardiac or pulmonary situations that make this set of goals un-attainable then you need to correct them as far as possible and accept the need for some serious amount of gear - O2 tanks, batteries for your'e pacemaker and the surgeon needed to replace them etc...