I think its more that the Star Trek writers simply lost the ability to create multi-dimensional characters. Michael Wong created the extremely apposite and descriptive term "brain bug" for this process. He defined it as "ideas start as an insignificant microbe and then grow of their own accord, gradually infecting the mind like a malignant tumour......They infected the minds of the viewing public (including these writers),where they grew and festered for years into bloated, monstrous masses of diseased tissue. The result was that with each spin-off, minor elements of earlier series were blown completely out of proportion and became self-sustaining mythologies in their own right. "

Gene Roddenberry originally envisioned the Ferengi as the Federation's primary foe, as part of the sea change in Star Trek's underlying theme, which was being revised from the 1960's Cold War to a left-wing liberal tirade against consumerism and capitalism. The Ferengi were not simply greedy; they were powerful, mysterious, and dangerous. Their appearance may have been odd, but these were clearly not people to be trifled with. Picard once recounted the story of how he lost his previous command, after his ship was reduced to a flaming wreck by a Ferengi warship. But in every appearance, the Ferengi made reference to a profit motive, and that was more than enough to plant the brain bug.

By the time the Ferengi showed up on DS9, their interest in profit had grown to encompass their entire culture. They were suddenly interested in nothing but the accumulation of wealth, and the writers' inability to conceive of a culture as anything more than a one-note joke meant that any non-financial elements of their society vanished without a trace. This brain bug continued to grow. Not only was greed now the only defining characteristic of Ferengi society, but the writers even made it the Ferengi religion! Instead of the Ten Commandments, the Ferengi had the "Rules of Acquisition", with which the viewers were bludgeoned with constant reminders of Ferengi greed. Instead of "astral plane" or "holy ghost", they had the "Great Material Continuum". As Michael Wong points out, "another society had been transformed into a farcical one-note caricature."

The Ferengi need to be redrawn to restore their original status as a powerful, mysterious and dangerous opponent. Again, we can use the plot device of Federation propaganda to eliminate the products of the "brain bug" and, instead, present the Ferengi as the reasoned voice of laissez faire capitalism. The nonsense about the Grand Negus introducing welfare-state socialism into ferengi society can be eliminated the same way (perhaps simply by a character remarking "Oh that con-man, he got away with his impersonations for a while but the police got him in the end. Still, it doesn't take much to fool those hoo-mans.")