Can vehicles benefit from obsessions in a mercenary detatchment?

Hypothetically, can a detachment with for example Drazhar as HQ and only incubi or scourges have a raider that benefits from a Kabal or Cult obsession? Or would I need to add at least one Kabal or Cult unit to do that?

Yes it would. You select the obsession, say Flayed skull. The vehicles and any kabal units benefit, the mercs don't. If it is only mercs and vehicles, the vehicles get it.
Pretty smart.
May steal this idea