[@AtomicNut], considering that a Noble Arm is born from personal development, including negative development, Damian's chaotic soul works as a one in a billion (or one in two billion) sort of 'functional madness' that acts as an exploit with how Noble Arms work (Formation and Inheritance, specifically).

Make it clear that it is an Exploit both ICly and OOCly, that Damian cannot take Noble Arms from a living person, and that when an Arms Master dies, he only has a few seconds to take their Noble Arm before it fades in a flash of light/motes of light/just fades away.

Edit: Or it could be that Damian can delay the fading away of a Noble Arm if it is within sight range (not sure if scopes and such should enhance this).