Ever since I saw how they are handling Gladiator stance, I got wondering on how blizz could work Berserker stance back into the game. Best way I think would be baking it into the DPS side of the talent line that has Gladiator's stance. In other words, it'll make it a stance based talent no matter your spec.
For example: Berserker Stance: Increase damage by 5% in battle stance. Changes Protection Stance into Berserker Stance.
Berserker Stance: Increase damage by 10%, Defense by 10% (needs to keep battle stances damage reduction or else no one would use it). Increases movement speed by 10% and haste by 10% (whatever is needed to keep it balanced with the other talents, damage wise). Recklessness is replaced with Wrath of the Berserker.
Wrath of the Berserker: Removes all rage costs for X seconds.