Regarding Ash, I've heard that... Spoiler: ME3 Codex According to the ME3 Codex (people have found the files for it), Ash was promoted to Lieutenant Commander following the Battle of the Citadel. If true, this is obviously a massive retcon, as Ash was an Operations Chief (one rank above Gunnery Chief) in ME2. And yeah, according to the Alliance rank system, Kaidan does officially outrank Shepard in ME3. But Shepard is probably still CO of the Normandy, so at least while they're both on the ship, Kaidan would probably follow Shepard's lead.