I think the execution really suits the Shinobi but it also looks weird as heck cause of the two chain-sickles locked on to his/her wrists, which makes it look very awkward when using the execution.

If there was some other way to hide the chain-sickles or put them somewhere else, then that could fix the look of the execution for the Shinobi. A similar way to how the 'I AM WAR!' emote hides all weapons, would be good in this case, but that may not be as immersive.