A) The wiki is incomplete and outdated in places. Just so you're aware. The editors either don't know enough to make it comprehensive, or don't care enough to write articles. There are also redundant articles, often with at least one version containing outdated information/generally horrible advice. But it is good for the basics, at least.
B) Unless you take certain mutations like nimble fingers, support builds don't sacrifice much, if any, combat ability, because whips is rape, and they have the advantage of being able to maintain their own equipment/administer medical attention to themselves. Even if you focus on non-combat skills, you'll probably still get your weapon (whips, unless you do something
retarded AWESOME like I am and have a blade/gun wielding brains build) skill pretty high, which means you can kill mobs for contracts like anyone else. And you should be able to, because crafting components are often in dangerous areas.
C) For all the talk, the game isn't
that brutal, though if you have a thin skin then it's not for you. The hardest part is the starting grind, because you make basically no money and can barely afford the bare minimum in equipment, making any loss potentially devastating. Once you've gotten past that part, though, money will come pouring in, and you won't really care about dying unless you were doing something stupid that lost massive amounts of money as a result. I crashed my plane at least once with a fairly low-level support build, and just laughed off the $20K loss (actually, much less than that, because lol insurance) (well, I did lose some implants, which probably brought the overall loss up to $15K or so, but I had $300K in the bank, so I still just laughed about it).
D) Support builds tend to be more respected, because it requires actually knowing what you're doing instead of just running around hitting things with point sticks in between blowing yourself up. People who can defib others, treat diseases/rad poisoning, repair weapons and install mods, or craft weapons for their corp/random people who ask for their help are comparatively rare.
How popular are scavengers? All these crafters, chemists and cannibals must be hankerin' for someone who can provide the necessary raw materials, yet something tells me that Junkratting may not be the most popular choice of lifestyle for the average player.
Most crafters are also scavengers, due to the stat overlap. Really, your role choices mostly boil down to brains build (who will be at least somewhat competent in medic, repair, craft, hack/locksmith, etc) who probably uses whips, and combat builds, which include most abhuman players and often focus mutations due to stat overlap with some weapons. Freaks can be medics, and provide support for aboms.
Also, reading around a bit on the wiki, it seems to me that inhuman players are a great big pile o' demand just waiting for a good supply. I imagine that dealing drugs to abominations and selling heads to zombies might make for some fairly decent business relations. Would I be wrong in assuming this?
Half. I've heard buying equipment for freaks and aboms in your corp can be fairly lucrative, but you probably wouldn't be in contact with them if you're not in a corp with them, and most of them tend to join the higher end dicking around corps, from what (admittedly little) I've seen. Zombies can just kill someone and eat their brain, so I don't think they'd pay for severed heads, which are quite heavy to carry around in the first place.