Fun Idea: Ethereal Warrior Monks (just hear me out)
Image: Of Aun'Shi, an ethereal known for is ability to fight and hold his own.
I don't know why but the idea of a special group of Ethereals who develop themselves into Warrior monks (akin to how Aun'Shi is depicted) has been bouncing around in my brain lately.
The idea that as the T'au Empire is engaged in war longer and longer, Ethereals have had to develop stronger traditions of combat for themselves. They'd obviously not use any weapons other than their Honour Blades as that would be beyond their caste. Addition to this, having their fighting style be 'strange' to observe like they aren't really 'fighting' in the traditional sense would be an interesting mystical way to continue build upon the Ethereals as a caste. Maybe the Ethereals have a strange way of fighting that the ever growing threat of Chaos and daemons have difficulty against.
Uncertain how this would impact Table Top if ever, but the idea of a warrior monk just bouncing around on Orks, Daemons, or even the Imperium gives me joy.