What if in one of the future expansions, there was a part where the enemies (depends on what expansion) steal your ghost. Since your ghost summons the sparrow and ship, it would be cool if we needed to manually do some of those things while on the hunt for our ghosts. To get a sparrow you would need to find a terminal somewhere and ride from there. For your ship, maybe a cutscene of you getting it from the shipwright, then you could manually control it on the decent to the planet. To open locks, maybe you need to kill a major/ultra with keys or access codes to unlock them. I think doing a couple missions without a ghost would mix things up and add interesting gameplay for anyone who is burned out.