Should most spirits (mostly thinking for good; KotD, WotD and RotD and for evil; Shade and Spectres) get a rule like the chittering hordes? To represent them moving through each other.

In regards to WotD I know they can get spears but this would remove the option but should they just be for aesthetics since they have blades of the dead.

Think this would power up these units for use as a single army, rather than have to rely on other armies to support?

Is this too over powered an idea? Does it go against fluff?