Nirn being a plane of oblivion was propaganda by Mankar Camoran. One of the major splits between Aedra and Daedra was the fact that they did NOT help create mundus, the mortal realm, home of the planet nirn. This is why the gods' physical forms are all either dead or became mortal and are the ancestors of humans and elves, while daedra are still immortal, and like toy with the world of mortals: A world they didn't create. Also, the other schism between aedra and daedra is the fact that aedra are closer to anu (order and stagnancy) while daedra are closer to padhome (chaos and change). Because of this, daedra can't create anything out of thin air like the aedra can. They can only change what already exists. While the aedra can create things put of thin air, but they lack the creativity the daedra have. My point is, Nirn is NOT a plane of oblivion. I just wanted to clear that up. Back on topic:
I doubt the Dwemer, if they returned, would ever work for the daedra. The dunmer hated the dwemer because they were blasphemous and spurned the gods, and didn't follow any religion ordinary people could understand. Due to the natures, they definitely wouldn't work for a god who represents order.
Wow, I just got schooled, apparently. I was under the impression that while yes, the dwemer didn't care for any of the aedra or daedra, they might be interested in an alliance with Jyggalag. Yes, he represents order, but that's roughly what the dwemer were interested in: order, and the following logic and reason that comes from it and using all of the above to transcend physical existence. What if they failed? I read a post someone added stating that the dwemer's souls were used to create the skin of the Numidium, but were they all used? If not, where did the rest go? What if the rest failed to reach that ultimate goal of theirs, and were stuck in some sort of weird limbo in some forgotten plane of Oblivion? Or, perhaps they aren't stuck, necessarily, whatever; point is, is that if they were to come across Jyggalag, while they wouldn't view him as some sort of god to be worshiped, they might view him as an entity of significance. An entity stripped of a great deal of his power, but poised to regain it, with personal goals that roughly align with theirs, the dwemer race as a whole. They might either ally with him to gain knowledge, or they might even attempt to usurp him and take what knowledge they could from him. There are countless ways in which some connection could be made between the dwemer and Jyggalag, and how it could bring them back to Tamriel. I honestly wouldn't care how the devs would do it, I just think it would make for a great story.
As for Mankar Camoran stating that Nirn was just another plane of Oblivion being propaganda, who's to say it isn't true in a way? After all, why can't it be a plane or portion of Oblivion that the Aedra contributed to and sacrificed themselves to make it more stable, more permanent, and more well-defined? If the daedra cannot create, and can only change what already exists, then how did they come upon their own planes of Oblivion? Did they pick a patch, post a flag upon it and say, "This bit's mine!" If that is the case, then who's to say that the Aedra didn't do the same with Nirn, making it incredibly tough for the daedra to tamper with it in the process? There's a lot of vague notions in each races creation stories, and while they roughly match up, there are some inconsistencies. And, after all, what we know was provided by mortal historians, not the aedra or daedra themselves. Who knows what Tamriel really is? Ultimately, it's whatever the devs want to make of it, and they can introduce new lore that can change all of what we think we know in an instant, and make anything possible.