...Which is because they violate the treaty and penetrate the Zone. Rearranging the specifics of the zone wouldn't help with that.
I wonder if the camera just chastely turns away when the Feds do their equal share of violating? (cough"Contagion"cough)
In the episode "The Neutral Zone," for instance, it's shown that there were actual Federation (and Romulan) settlements there, which were the first to be assimilated by the advancing Borg.
Naah. The Federation outposts that the Borg have scooped up are only said to be "in this vicinity", not within the Zone. During the episode, Picard never actually moves into the Zone. The Romulans do (Picard: "Commander, you have crossed the Neutral Zone. This is Federation territory."), but it is all forgiven when they explain themselves.