Well, there's not a whole to upgrade. Enemy ships already die in one hit, so unless they provided bigger targets which require more hits to kill, the weapons and shields systems are out. The ship doesn't need to go faster, as travel is mostly instantaneous. Maybe the addition of furniture? Lockerooms for stuff you don't need. Hologames, maybe? Not much else that I can think of. Maybe you could run cargo missions and you'd have to enlarge the hold?
"HAR HAR! I shot down another starfighter... oooh, lookie here- he had a sofa in his tiny cargo hold."
uhm. don't think so.
it'd be nice to be able to do more with the ebon hawk though. y'know buy upgrades etc.