A interesting secondary feature Ghosts could have would be acting as a player controlled recon camera. The MAV in BF3 can be pretty useful in multiplayer and lone wolfs running around Destiny could benefit from being able to pin point Ai routes and strengths. Plus it would be a cool feature regardless.
Plus after watching the demo being able to safely navigate a structure that might be bathed in radiation could be a fun mini game trying to avoid the Ai's drones in order to unlock a hidden door or some switch that allows the player to advance.
Hope you guys considered it as a Option for perking this specialized companion.