The only rational intestellar conquest scheme I can paint for Aggressor is a plan to take over Victim, uplift their society to the point where they could actually productively contribute to Aggressor's (no doubt technology, service and innovation based, as our own) economy, but keep Victim from ever developing the means of becoming a threat and an aggressor in their own right.
What on Earth makes you think that these sorts of conquest schemes are
rational? Or that economic considerations are the actual motivations?
Seems pretty obvious to me:
The object of torture is torture. The object of conquest is conquest. The object of power is power. The object of sadism is sadism.
The Cardassians didn't conquer Bajor because of economic desperation any more than the United States invaded and occupied Iraq because of national security. They did it because they could.
I don't want to get into a whole thing about Iraq, but whether one believes there were
compelling reasons behind it or not, there were
reasons, even if the reason was as simple as
spite (which is not per se irrational).
At any rate, even when an eeevil nation invades another for reasons of pure conquest (which
is still a reason) it ordinarily does try to utilize the new resources in a more-or-less rational manner, at least if it's modernist in outlook, which any self-made warp power is almost by default going to be.
Chattel slavery and work camp slavery are not really rational uses of an advanced society's conquered resources. Running a labor camp is likely to cost more than using machines to do the same crap work.
Timo said:
To be sure, the latter already has plenty of Trek precedent. Why would Bajor and Cardassia need to enjoy a special (pre-)historical connection when for example Klingons and humans interbreed without one? We already have a general solution (from "The Chase"), why try for a special one?
Because Card/Bajoran interbreeding is the only one I know of that can't be handwaved with medical intervention. <_< (Well, it can be, but you have to
twist Dukat more than Season 7 did to do it.)
In terminology at least, Worf's old home Gault was a UFP farming world. And creation of worlds of that type was the goal of Carol Marcus in the Genesis project.
Maybe the Amish ran Gault.

As for Genesis...
Firstly, it was before replicators (even if Genesis was, really, the apotheosis of replicator technology

--maybe it's like the difference between an H-bomb and a Mr. Fusion), agricultural trade may have had a greater significance than later.
Secondly--and this is critical--taking the alleged fact as true, a stated intent to use the Genesis device to create farming worlds does not necessarily imply an interstellar agricultural trade. Even if the idea was to build world-farms to feed
Earth, Genesis would be most profitably used on
Venus...
Hey, why the hell didn't they test it on Venus? Is Star Trek II telling us that there is life on Venus? Europa? Titan? Interesting inference, I think.
The fact that relatively recently founded colonies tend to be agricultural is probably unrelated to the issue of "farming worlds", I agree. Then again, it could be that specialization does pay: certain colonies expand their original sustenance farming into an export business, while others export mineables and probably have to import foodstuffs as a consequence. Such export-dependent economies can only be abandoned after these colonies accumulate centuries of experience, wealth, population and infrastructure, after which we get something more like Deneva.
Well, the lithium miners probably don't grow their own food, I agree, but they probably also get their entire contract's worth of food in one go. It's not like they're ordering Domino's. It would be impossible to avoid the Noid at that distance.
You know, it may be interesting to point out that TOS had humans running automated or nearly-automated mining operations in the 23d century. Makes the Cards' insistence on relying on Bajie scum on Terok Nor, if not on Bajor itself, even more perplexing.
Now that's a hairier issue than the ones about minerals or food or slave labor...
How could Organia be "strategically placed"? Why would the Klingon Empire or the UFP covet a planet that can provide them with nothing except some bedrock and air?
Actually, you got me there. I just threw that in there because I was sure if I didn't you'd point out that they
did covet Organia.
Even with dirt cheap warp drive, I find it hard to believe that even the most audacious exodus of Cardassian citizens would be anywhere as effective in controlling the population problems of Cardassia Prime as the least ambitious campaign of contraception. Colonization of space isn't a solution to population issues. It's a conquest campaign, a means of getting rid of the excessively eager, a way to reach raw materials, an issue of prestige. It's not a viable sink for great numbers of excess people.
You're devil's advocating here

--warp drive can't be so cheap that it permits interstellar delivery of foodstuffs yet too expensive for colonizing efforts, can it?
Minerals. That's quite solidly established everywhere in Star Trek: certain substances only exist on certain planets, and by far the easiest way to get them is to go to those planets and extract them.
Replicators might get the same thing done, yes. But at greater energy costs, and at the expense of other things to be replicated. And if you manufactured your own dilithium, this would mean that somebody else would get to mine the dilithium from Motherlode IV. You can't have that sort of thing happening!
Overall buyable.
I wish they'd keep the number of unobtainiums to a mimimum, though. Dilithium is fine. The crazy made-up metals that to all outward appearances do the exact same thing as real metals gets under my skin a little.

(Subatomic particles, too.)