"Waystones can also be implanted into machines, and the consciousness they contain becomes the controlling element of the machine, allowing the Eldar to live again in a new form."
"When the Eldar go to war they are frequently accompanied by the dead in the form of Wraithguards and Eldar Dreadnoughts."
That doesn't sound so bad to me.
Exactly my point, the Eldar are phobic about saving the souls of dead Eldar but they don't seem to have any qualms putting way stones into service in... let's face it robotic units that tend to spontaneously explode (read wraithguard), releasing the soul into the clutches of Slannesh.
Don't they have empty way stones with a copy and paste function?