I'm pretty sure with Sheogorath, the CoC did become the prince himself. Notice how the realm of SI suddenly went back to being SI again upon Jyggy's defeat. Remember, the prince is the realm, and the realm is the prince. However, Sheogorath is a very special case.
But you are right Talos is not an aedra. In order to be an aedra, you had to have been one of the original spirits (et'Ada) that gave a part of itself up to create Mundus. Talos didn't, he only ascended into godhood by mimicking events from the past, in this case the one about Akatosh-Lorkhan. Also to note, Talos is only a replacement for Shezarr (the Cyrodiil Lorkhan, who is revered by the Cyrodiils).
Also, do not buy into the mer's view that the aedra were tricked. The mer are so full of themselves, they make the people in San Fransisco, in that South Park episode, look like one of the most humble people in the world.
You have to ask yourself though, what is a Daedroth? The creation of the Daedra is fuzzy on most accounts, and certain Daedric Princes don't seem to fit the mold (e.g. Meridia, Sheogorath, Malacath).
If Talos is a replacement for Shezzar, (as in he takes Lorkhan's spot "in the sky" that he lost when his heart was ripped out) why do Shezzarines still pop up on Nirn? In fact, how would he become Lorkhan at all? The key events Shezzarines reenact are:
-Tricking others
-Getting betrayed
-Getting de-hearted
Now Tiber was definitely on par with the best of them as far as manipulation goes, but I can't think of any situations where he was betrayed by those he manipulated, other than the instance of his throat being slit and almost dying. Even then, it wasn't as much of him being betrayed but instead more of a political assassination. By the way, how did he ascend? It was at Sancre Tor, correct? It would have to have been after his joy ride with Numidium too, I suppose. What too, was the fulcrum he used to propel himself upwards?