Just thinking aloud here.... but what if picking Rage gave you two buttons instead of one (kinda like how Swap Ammo gives you three)? You have have Rage (standard click, non-stackable, no crash or penalty) and you have Double Rage (toggle, decent cool-down, high end-cost, boosts Damage even further like a second stack of Rage but comes with a Def/DamRes penalty). Then you can have your usual Rage while stomping around and yet have some extra oomph if you need it, but you will pay a price for it. (You might be able to mitigate the End cost of the toggle, but the hit to Defense and Damage Resistance is going to be felt regardless.) Just a thought. YMMV.