Yes, it would be up to the devs, but this would then require traders, explorers, miners etc to carry a KWS at all times? Currently this is not required (or even useful).
You MAY win an interdiction against a CMDR, but with the current system of interdiction, the balance is HEAVILY in favour of the interdictor. I'm certain you know this. The only time I submit against an NPC is if I'm armed and want the bounty (or in my Type-9 and can't be bothered with the time it takes to win) - all other occasions, NPCs can easily be defeated in the interdiction minigame
This may be lost in translation, as I'm not quite sure the point you're making here
True, but for a "ganker" sitting in supercruise at a high traffic area to see a "blip" appear on the scanner, turn and scan to see if it's a CMDR is only a minor inconvenience. For the CMDR arriving in the system and seeing a dozen or more "blips" and having to scan each one to see if they're in danger, much less so. Again, the advantage here is far more in favour of the "ganker".
As has been previously pointed out, a "ganker" will tend to have much more experience in spotting the difference between an NPC and a CMDR than a potential "gankee". I also refer you to my point above - if the "ganker" has already scanned every ship in their instance, and another arrives, it's trivial for them to simply scan that ship, discover it's a CMDR and attack before their victim has even scanned the first 2 ships in their instance. The advantage weighs heavily with the "ganker"