Let me ask you this: Are roving bands of high level players ganking greys a net positive or a net negative to the health of the game or gameplay in general?
In my opinion, this is part of a PvP server, but the environment is only enjoyable with a reasonable (3k or less) and balanced (55/45 at most) population. I don't recall ever being in a "roving band", but I've certainly been killed by them. And I've done my fair share of personal revenge & protection kills on greys.
Now we need to ask the roving bands the same question as they also make up part of this server.
WPVP to me at its best:...
W'PVP" at it's worst:...
Sorry, man, but these are opinions. Opinions I'd be party inclined to agree with, but still opinions. On top of that, every instance you listed (best and worst) is all under the big umbrella of the PvP server, always has been. I'd say stop wasting your time thinking about the psyche of lowbie gankers.
I'd also say:
PvP servers at their best: people understand and accept it's a PvP server and understand and accept everything that goes along with it without complaining, otherwise they understand and accept that PvE servers exist and play there instead.
PvP servers at their worst: not that.
What negative impact would perhaps a hit across the board (Rep and Honor) for killing greys in contested zones cause? What negative impact would there be if ALL flightmasters were shut down for individuals for a period of time when they take part in killing one? (call it a FM Union)
Question 1 might be worth a pole, but be prepared to get laughed at. I don't think it's horrible, but I understand and accept I'm not part of the majority of pserver players.
The FM union or something similar is a good idea--I really like it--but honestly I think the "griefers" would be able to cope with it (hearth, mage ports, eng trinkets, etc.). On top of that, there's a chance there'd be more of them on mounts out in the world because they couldn't fly anywhere.