Sure, but armor doesn't stack unless specifically noted. So say you put an armored vest on a Nissan Oni; it now has Armor 10, or Armor 2. Pick one.
There's an obvious argument to be made for things like elemental protections, but if a player really wanted to add those to a drone I'd let him (this is not RAW, by the way).
RAW, you probably have to wait until the Rigger book comes out, at some point.