Also, I really love (and I think I understand) what Megaton Hammerstein wrote.
I don't think there is a hard and fast rule as to what can be called a "god" in The Elder Scrolls. The Aedra are one definition that exist the way they do because of the way Nirn was created. Daedra are a different definition that is not directly connected to Nirn, but still interested. The Tribunal embody another possibility (or more than one if you read Vivec's writings closely). Talos embodies another. I think Michael Kirkbride even referred to the Nerevarine as possibly being able to fulfill the basic definition in the page I linked.
I don't think there are solid answers. Even for those who experienced these things, they are as much philosophical speculation as they are fact. I also think for some of these beings, the same concept or event could be either fact or speculation depending upon how one looks at it or wants it to be.
I'm not trying to be difficult, but the majority of writing on this sort of thing has a very philosophical tone, and most of the writers are either mortal and not fully equipped to explain it properly. Or they're divine in some way, and their explanations and instructions are probably biased in some way by their perspective. Vivec, for example, created an entire myth cycle around his early life as being destined to become Vivec the god. In some ways, this cycle is probably both true and false, or at least was while Vivec was still a god.
So the best thing you can do is read things like Vivec's Sermons, the Five Songs of King Wulfharth, the Arcturian Heresy, and other relevant books, and discussions here and come to whatever conclusions work for you.
I do think it's pretty unlikely that anyone has ever been or will ever be elevated to godhood by any of the Nine Divines. I don't think they function on that level.