Personally, I'm fine with the martial classes all being absorbed into a generic class, but allowing versatility to happen through class features.
I don't think that you could have barbarian and fighter be meshed that easily though.
The fighter that follows the "barbarian" path would be more a fighter that uses rage to fuel his fighting style, but does it in a trained style. Giving him the rage ability wouldn't make sense, the fighter is a discplined martial warrior. The 'angry' fighter path would instead get power attack, cleave, and maybe the ability to enter into a "rage-like state" where he gains bonuses to attack, at the cost of his AC, up to 1 point per 2/levels or something along those lines. The idea is that it's a manuver the fighter can use.
I also haven't read ToB, don't own it and have no real desire to, so I can't comment on those fixes.