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Seb-wejem
The background changes are pretty much mechanical, though. It allows you to take the soldier/guard background, but swap a skill proficiency to arcana if you were say a guard for an archmage in Halruua(sp). I think that sort of thing is great to leave in the players' hands.
I'm talking about completely changing the fluff of a class from being a Barbarian, to being a Mean Drunken Master or Angry City Guard and having nothing to do with being a barbarian at all. That's not just an unconventional barbarian, it's becoming no barbarian at all.
We already have "non-barbarian" barbarians in the game though. The dwarven battlerager doesn't come from a barbarian tribe, at least the only examples I've read about is that they are a specialist warrior class amongst the dwarves of Bruenor and the zealot could be from any background that follows a war god that divinely inspires their rage.