That puts them ... not close to parity with the Federation.
They can't do an all-out deployment because they've got "vassals" who would knife them in the back given a chance.
The problematic vassals are the Dawiar, the Konen and the Bajorans.
The Goshawnar seem to be content acting as Cardassian battle thralls, probably because the Cardassians are happy to let the Goshawnar fite as long as they don't fite Cardassians. Plus, the Cardassians successfully installed a puppet government; it would take a major defeat of the Cardassians' power to make the Goshawnar restive.
The Dylaarians seem unlikely to upset the apple cart, especially since they're not actually being enslaved or brutalized or anything as far as we know. Though some more intelligence on that would be nice.
The Lecarre seem content with the status quo, though they may change their minds when the Qloathi and Seyek join the Federation and bring Federation borders very close to their space, increasing their vulnerability to conquest.
...
The Bajorans, well, their traditionalists are anti-Cardassian, but their 'reform' faction (the one trying to end the caste movement and secularize) is probably pro-Cardassian. Either way the Bajoran Navy is going to be tiny and they don't have the kind of highly experienced planetary guerilla force we'd see fifty years from now, so their ability to make trouble for the Cardassians is limited. They're not a problem and probably require little or no special Cardassian ship force to control.
The Dawiar are a problem because their strategic situation has become entirely untenable. If they were closer to Cardassian space they might well remain loyal clients, but their loyalty is uncertain given their position. They would probably honestly be better off at this point as friends of the Federation, and at least some Dawiar are likely to know this. However, they're unlikely to rebel- just to
leave, and in the process of leaving wouldn't necessarily tie down Cardassian ships.
The one affiliate species with a significant fleet, that is likely to rebel, is the Konen, since the Konen were straight-up conquered in the relatively recent past. I would definitely be worried about that if I were a legate.
In wartime, the obvious way to deal with this is to coerce the Konen into contributing ships, then have these ships be worn down in combat on the front lines of the war. As long as their military power declines faster than the Cardassians, they will be unlikely to rebel unless the Cardassian Union is broken up so thoroughly by the war that it becomes unable to launch a post-war punitive expedition. It's only if the Konen
avoid committing ships, and wait until the Cardassians are worn down to a level that might make it possible to regain their freedom, that the Cardassians are likely to have a serious problem with a Konen revolt.
...
Meanwhile, the Sydraxians are no longer really Cardassian clients
at all, and the Yrillians are at best dubiously likely to do anything significant against the Federation though they may tie down some Federation member world assets that are trying to keep an eye on them.