How about this - an exo armor that grants: Friendly fire can pass through bubble, but 50% of damage is applied to the bubble, and 50% to the target. Bubble collapses when its HP are done. So the more you take advantage of it, the shorter the bubble lasts, and no OHK's from inside a bubble due to 50% nerf. Also, if using power weapons inside the bubble, it will collapse faster still.