Crafters, Wasteland Guides (a.k.a. "Taxis") and any type of "peaceful" character would have a boring and frustrating life.
Imagine that you're 3rd level armor crafter and just crafted bazillion BAs and you encounter character that is 1/3 your level but he chose combat build. He rips you to shreds, takes effects of your hard work and you respawn w/ 98765432345678 minutes of crafting cooldown.
Of course I agree that this would encourage more RP gaming, better cooperation between players and a natural neccessity for specialists in big factions. This all looks good when we write about it here but "I have a bad feeling about this", to quote Star Trek catchphrase
I disagree. Just because a player wants his only char to craft something, doesn't mean he HAS to use a shitty build for that. Also, not all leader/taxis suck at combat (I am sure that people like Vedaras or Michaelh139 would agree here). Also I believe that if you are a pr0 PvPer against a player not so experienced in PvP as you, you can defeat your oponent.
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You have to be aware also of people who will come a great legth just to cheat in a game and be better than anyone else. I can bet anything that there would be some players with alts that managed to bypass the limitations somehow.
Well, in my hopinion one character per player would make the game more "MMO". There should be the possibility to make a crafter with decent combat skills, at least for fighting weaker NPCs alone, but still unable to make any resistamce to Unity and so on (Jhans should already be a problem). Having one char per player would basically make player's social skills very important: as you said, crafters will have the economy power, and fighters can offer their protection. Gangs also will have more sense. There will be crafters, hunters and fighters according to everyone's favourite way to play the game.
The only problem is people who are not in the big gangs. The popular gangs will never have any problem as they will always have the dedicated 1 int 1 cha power builds and the dedicated crafters.
This game was firstly developed as "Faction Mod" and (guess what) it was always focused on big gangs/factions and still is. That's why solo player would never be able to compete with organised groups and crafter-combat would never be able to compete with pure combat "1 CH powahbuild OMFG", whatever nerfs are about to come.