I think the best approach is to build a core supply list, then augment or change as the needs change. You simply can't build a kit that is universal, because needs change enough from one situation to the next that comprehensivity is not a practical objective.

That said, my core kit includes an FAK with some Ibuprofren, Aceteminophen,aspirin, bandaids of various sizes, feminine pads, latex sports tape, disinfectant, antibiotic, and some wipes. Then I pack a leatherman wave tool, a magnesium/flint striker, a butane windproof lighter, a bivy sack, a couple plastic trash bags, some ziplocs, some water treatment pills, a sewing kit, a tongue depressor with electrical tape, duct tape and 120 lb dacron fishing line wrapped around it, a fox micro plastic whistle, a map compass, some paracord, a few tea bags, some HD aluminum foil, and some Couglans cotton tinder. I'll augment that with everything from water ration to food to a Glock 21 and a BAK to clothing etc... it depends on the situation(s) I am likely to encounter.

All the core kit fits into two small nylon padded satchels with good strong zippers. Each satchel measures 6" x 2.5" x 2.5", and were acquired while flying business class to and from Baghdad last year. I can load these satchels in the front pocket of my SAK business bag, which holds my laptop and a few other business and personal items, or I can put them in my Camelbak Motherlode BOB, or I can load them in the cargo pockets of my REI expedition pants, or I can attach them to my belt when I wear my jeans.