Just did an assassination with a G5 Executioner using the above mod. Should a long-range kill shot (out of sight of guards) give me a wanted status with the local faction?
Yes. It's the omniscient police force again.
Worse, it's like an over complicated version of what we encounter in ships.
Ships - take out a Wanted target, but wait for the scanner to show the wanted status, everything is fine. If not, you will get fines and/or bounties.
Foot - Passive scan isn't enough. You need to use that short range hand scanner, equivalent to a kill warrant scanner, to scan the target. If you do this, and the target is wanted, you can kill them and not become wanted. However, if anyone nearby sees this, they will become hostile (unlike in space).
So if you're going to take out a legally sanctioned (aka their wanted) target at a non-anarchy station, you'll need to do a hand scanner scan of them first to determine that wanted status. Worse, you need to do this out of their line of sight, or they will go hostile and immediately open fire once you discover they are wanted.
Again, while I think the difference is dumb from a lore perspective (why is it easier to kill wanted ships than a wanted person on the ground?), it does make it kind of fun. Kind of like flipping out a badge and telling them they're bound by law... and then you shoot them, old west style.
If the target isn't wanted, your screwed. Just kill them however you can and deal with become wanted. Try not to kill anyone else, as it only takes 2 or 3 kills to get a 1 in notoriety.