No, I haven't. It sounds fascinating. I have always speculated on "how far" Imga have developed as an independent culture and people. Theres very little known about them, besides some slightly comical comments about their ridiculous attempts to "emulate" the Altmer (whom they seem to have an avid fanatical loyalty to) - To this effect, I can see Imga being a real headache for an Imperial offensive into Valenwood, since they seem to be diehard Altmer (And therefore dominion) loyalists. They are also probable numerous. But again, of limited intelligence, since they have never emerged as a new civilisation. They are basically witty gorillas (liked the smart crack, by the way ) who can dress up. But they are also pretty scary in a fight.
Ayelids and Snow elves would both have good reason to hate the human races, and to fight against them rather than the dominion (to which would constitute almost zero advantage). I imagine the dominion would like to install an ayelid government in Cyrodill, as a vassal. Of course, that's if they even exist. But there is speculation that they do. Snow elves...I cannot see them ever fighting for the Empire, after what went on with the Nords. Theres a possibility the dominion would offer them a significant chunk of Skyrim if they fought for them. Do they actually like the dominion? Hard to say if most of them are even aware of what is going on. The Falmer, if they continue to develop, are going to be a major threat to Skyrim in the future. If they could somehow be engaged....it wouldn't be gorilla fighting, it would be an all - out war for supremacy in Skyrim. It would basically be the end of Nordic help in a second conflict with the dominion. But again, im not sure the falmer are intelligent enough to even care about it.
Dwemer are a politically isolated bunch historically. Even if they returned I doubt they would even care about the great war...mainly they would use it to their advantage to conildate a strong position on Tamriel.
Other races? Most of them [tamrielic] are extinct, or have left forever. I cant see them playing any significant part in future conflicts. I think Sloads are perhaps the one force Imperials could use to their advantages....give the sloads alinor if they launch an inward invasion. It would be the equivalent of a snow elven invasion of Skyrim.
For me, besides Snow elves, I see any intervention by lost races to be extremely unlikely. But it cannot be rules out.