The things that kill in the bush...lack of water, a blister, a splinter, (and for me personally,a migraine). Lack of water is obvious- but a blister in the shoe will stop a tough man from walking, so will a splinter. A splinter in a finger basically takes one hand out of operation. I now carry- extra strong glasses (so I can see what I am doing), a couple of endocet tabs, a (sealed hypodermic 23g) needle and tweezers and a suitable supply of plasters. I also always buy a few of those 6hr energy shots when I am in the states.
Yes, we are prepared to fix broken limbs, gun shot wounds, and treat typhoid - but it is surprisingly small things that cripple, and a crippled man cannot function well enough to 'make a plan'. I haven't had to plug a gunshot wound since 1998, It is nearly as long since I had to carry somebody with a broken limb, but blisters, splinters, headache...thats almost weekly.
I agree- it is fun to prepare for the worst in the areas you are interested in - firearms and medical for me' but a broader plan to cover more areas, abet at a shallower deapth, is probably wiser in the long run - You will probably never need a whole field hospital- but you WILL need a simple first aid kit. You will not need a whole truck full of spares, but you will need a spare radiator hose, fan belt and a few bits of wire (and if you own a landrover a 1/4" whitworth and a no 8 spanner). You will not need 30 guns and a truck load of ammo- but you will always find good use for a 12g, a .22 and a decent handgun...etc