The idea of the same card costing different for different factions has been floated before, and I actually think it would be pretty simple because each faction has its own official points PDF.
For example, "Moldy Crow" already says Rebel or Scum only. Additionally, the points listing is not found in the "Generic" upgrades list, but rather separately in each faction's document. Thus, it would not be that confusing or difficult for "Moldy Crow" to cost 15 points for Rebels (because their abilities trigger from having friendlies in arc) and stay 18 for Scum (because it is way better to have abilities trigger by having enemies in arc).
Looking to the future, Starbird Slash will be a far better card on a Resistance RZ-2 A-Wing, because they will be able to zip through a ship, and then swivel their arc around to fire. On the other hand, for an RZ-1 A-Wing, odds are if they zip through a ship, they will NOT be able to also shoot at it. Thus, the card will probably be twice as valuable on an RZ-2 than on an RZ-1. RZ-1s, sure, may be able to sloop or K-turn and have a shot, but that will be way more rare than an RZ-2 being able to do any maneuver, grab a mod, and then swivel the arc.
I know there is value in simplicity, so I do not think this approach should be taken for truly generic upgrades (like proton torpedoes, hull upgrade, Gonk droid, etc.), but given how few cards are (1) super specific and (2) faction-locked or chassis-locked, I think having separate costings for things like "Moldy Crow" and Starbird Slash would be a benefit.