Thanks a lot for all the ideas, I'll save this text so I can review this through the development, if I feel right I'll implement some of this features.
I loved the 5 topic, and we have right chances of getting this in game. I need a way to make Haki builds more viable, and this can help with this.
If you want to make the Haki build more viable, how about an active combat skill named "Armament Haki", maybe it could boost defense at the cost for damage output for a few seconds, this way you are able to better endure until the cooldown of your other skills runs out. This would also fill up the fourth skill slot which is currently unused.