When Rukia gave Ichigo her powers, he took them all because of his Quincy stuff. Maybe it sort of copied Isshun's zanpakuto, aided by his inner hollow, and that's why they're so similar?
Did he have an inner hollow then? I thought he got it during the recovery from Byakuya's attack/Urahara thing.
As a DM, I deal with character death by cheering and giving a fist pump, or maybe a V-for-victory sign. I would also pat myself on the back, but I can't really reach around like that.