The Opposing Democracy would work for the Romulans, the Cardassians would be the Military Dictatorship, the Klingons being the Space Samurais.
That leaves the Ferengi open as basically the MegaCorp enemies of Trek. Basically take something like Weyland Yutani and make them a Trek enemy/presence. They sell routes for shipping lanes, to anyone who has the money (including Pirates), they sell weapons to anyone who can afford them (thus meaning if both sides can afford, the Ferengi will keep wars going for centuries as it cuts them a profit and neither side may find out what's happening), when you make a move on them they respond by taking control of a major resource trading network you rely on so you HAVE to back off.
Basically, have their power come from everything EXCEPT military dominance.
Presumably they'd still need a rather impressive military. Contractual enforcement requires force of law, which is ultimately force of arms--and the great mercantile marauders of the past (like the Ferengis' in-Farsi namesake) all significantly outgunned their less sophisticated opponents.
A germane question is if the Ferengi, at this point, actually could
be rehabilitated into a non-laughable threat.
As for the Cardassians, they can't be the military dictatorship anymore, what with the complete destruction of their government.
Of course in the novels we have a Romulan Empire effectively prostrated by civil war (isn't that more of a Klingon thing?), so they can't really be much of any kind of threat, ideological or otherwise.