Ghost Rigger you appear to be giving me rent-free living space in your head. Too bad I can't physically live there and save a whole bunch of money.
Anyway, on your Five Scenarios where armor "literally" does nothing:
1) DV so high no armor in existence could have helped: Ok, not sure if DV was a typo for AR or a synonym for damage.. but either way: No Drek, Sherlock. If you're on the receiving end of an attack that enters "irresistible force" territory, then obviously armor doesn't help. Nor should it; can we agree on that?
2) Imaging Scope: The Scope may be preventing you from gaining edge, but A) you're forcing him to spend an aim action for no other benefit in order to get that effect and B) your armor is still able to DENY your attacker edge. That's still 2 more things than "literally nothing".
3) Attack was so wimpy your raw Body stat generated Edge on its own: sounds like the kind of situation where, if you have armor on in addition to the attack being pitifully weak to begin with, counts as a factor in your favor for the circumstantial Edge point?
4) Edge gain cap already hit: True, that sucks, but there's no cap on Edge gain denial.
5) Attacker's edge gain cap already hit: The inverse of 4) applies here. Just because your attacker can't gain edge doesn't mean that you can't. Unless of course...
6) The implicit argument of maybe 4) and 5) are both in effect: Ok, sure, this is a corner case where armor is potentially mechanically ineffective. To that I have three things to say A) It's a corner case; it won't happen very often. Yes, really. You really shouldn't be making all THAT many attacks per round (usually) nor should you usually be faced with all that many attacks per round (grunt group rules are intended to be used). B) You can always house rule the edge gain to "other than per round". Yeah yeah I'll see your "But but Oberoni Fallacy!" comment and raise you with "Frag Oberoni. I don't care." Furthermore, there's C) Who knows what Errata will come to address the edge gain cap problems. Maybe you, rightly enough, don't care yourself about B) and/or C). And that's fair. Even so, A) should still be enough.