Leila, if the Cardassians guarantee Celos but don't invade in force, we win massively. If they DO invade in force, then THAT should be the trigger for the State of Emergency where Sousa appoints herself temporary dictator for the duration of the crisis. Not the Cardassian declaration itself. Especially since the Cardassians themselves aren't going to care much about the difference between High Alert and SoE.
If the Cardassians hit us with a puny pinprick, or don't invade at all, there is no emergency to declare. Not on a Federation-wide scale.
There's just one planet, and a Cardassian sympathy card that will be small consolation as T'Lorel orbitphasers their coup government into oblivion.
At the risk of coming off as being too blunt, I think that's waaay too naive, and way too risky.
I think you're underestimating Cardassians as a totalitarian regime that puts a lot of actual stock in appearances. While you're right that Cardassians declaring for Celos, but not invading, would be a coup for us, it actually makes it
very unlikely from Cardassian perspective.
They're not stupid. Lying fascist spoonheads they might be, but it isn't actually rocket science to understand how weak it might make them look. If they fail to follow through on their open promise, the image of Union suffers, and Federation gets a free diplomatic card of "CARDASSIA PROMISES YOU THINGS; DOESN'T FOLLOW THROUGH. UNLIKE US." It's going to leave them even more politically isolated,
in addition to showing their hand that they're willing to oppose us.
They literally stand nothing to gain from doing what you're implying, and from their own perspective no less, hence why I find it uncompelling. I mean, it is not an absolute certainty, but the odds don't make me want to take that bet.
What I like about the option I was going for - and what Leila and Derek alike put in - is that we will already have the groundwork done for declaring the SOE, and in war the side that can generally process situation faster tends to have an advantage. If they actually decide to bow out and do nothing, then the whole thing doesn't go anywhere.
Again, I'm remain unconvinced of throwing away reaction/marshaling advantage over plausible-but-nebulous high ground.
And if Cardassians actually declare for Celos, but end up not being in position to support it, well tough shit; they'll have to deal with our home fleets rolling out. Which can be still transmuted into political advantage.
"Hello there friends. We heard you want to be friends with Cardassians. But we're asking you to reconsider. Consider Celos. Cardassians meddled in our affairs to support it, actually failed to follow through with their word, and ended up irresponsibly getting into a war unprepared. Is that kind of ally going to protect you? Are they worth dying over?
Also, consider we don't take protection payments."