Okay, so I'm looking at the numbers, and here's what needs to happen in order to make an intervention viable:
1. The HoH has to agree to a stop on the coreward border. Because they badly want to intervene, they should understand that intervention while keeping our our little diplomatic slapfight going represents a serious split focus and indeed, a lack of true commitment on their part.
2. The Council factions in favor of intervention need to be united in favor of intervention and in favor of punishing Cardassian action. In other words, the Pacifists, Hawk, and Expansionist parties need to close ranks. Between them, they have 36 out of 62 seats, a substantial majority. Out of the highlighted factions that might break along species lines, Tellar has 4 Development and 1 Pacifist, Vulcan has 4 Pacifist, 1 Development, and 1 Hawk, United Earth has 2 Development, 2 Hawk, 2 Expansionist, and 1 Pacifist, the STO has 2 Development, 3 Expansionist, 1 Hawk, and 1 Mercantile. Net, that means -7 votes if they all break along member lines, so 29 out of 62 seats. That means those United Earth and STO Councilors, and the Tellarite Pacifist hold the deciding votes, even with the Vulcans against.
3. We need to be able to take dettering action against Cardassia that isn't an invasion. Fortunately, we have a perfect place to do so: Bajor. If the Cardassians conquer Chrystovia and we respond by liberating Bajor, they've lost overall. Put that idea in their heads and that's our best chance of getting them to back down. Take action on that idea and at least we've made something good out of a shit situation (and triggered a horrific war, but principle, principles!). It's also viable because we can sell it to the public not as an invasion but as a liberation. We need to immediately get in with our affiliates the Bajoran Diaspora and get them more active in Council and especially in public lobbying, and to make it very public what we plan to do if the Cardassians continue their aggressive policies.
PRESUMING THOSE CONDITIONS, and also presuming that the Amarki relax the 25% rule, here's what I think we can muster:
4 Excelsior-A (3B)
2 Riala-A
1 Basillica of Lakhept
1 Constitution-B (B)
7 Renaissance
6 Centaur-B (2B)
2 Kepler
8 Anacail
Keep in mind this is all napkin work, not some idealized force composition, in an ideal world we'd be doing a shuffle through the sector fleets to ensure that ships arrive in time. I basically send the Apiata and STO ships home, broke up a few task forces, and filled in for the ships going home with unfederalized Rennies from the O4, and other ships from Rigel and Amarkia. The total force would be C154 H118 L167. This force would require the following portion of the Cardassian Union Navy:
1 Tolkor C9 H5 L9
8 Kaldar-II 7 5 6
8 Jaldun-II 556
8 Takaaki-Combat 433
4 Kapit-Courier 334
2 Kapit-Science 213
C153 H123 L151 - again, napkin work, okay? Don't pick nits here plz.
According to our latest reports, this leaves them with 30 Jaldun of both types, 4 Kaldar-II, 2 Lorgot, 11 Takaaki of all types, and 4 Kapit of all types. The big problem is the massive Jaldun fleet remaining, however this is their garrison fleet, so I suspect they may only be able to bring <12 Jaldun-class to bear on the Chrystovians, likely backed by the remaining Lorgot and Kaldar as those ships comprise the Cardassian mobile reserve. When we add in an ISC group and a HoH group, we have them.
The Task Forces that are maintained are:
8 ships on Beyond - again presumes significant drawdown is possible due to an agreement with the HoH
8 ships on Dreaming
9-10 ships on Royal
7-8 ships on Goodfoot - securing Ur'razzi cooperating is even more necessary with a possible war in the Bajoran corridor
This drops the Ittick-Ka task force and maintains the exact same sector garrison.
If we can pseudo-SOE it with appropriate Council legislation, we can commit a lot more force.