There's been something on my mind for many years since I've started playing the elder scrolls series and I would like to share my personal point of view of the TES universe. Since all possible endings within the franchise is canon due to the events in Daggarfall, an idea I've been playing in my mind for a while is something that follows these lines. I believe that the playable character is a forgotten Daedric Prince of Fate, Time and Curiosity. This is purely a personal theory and not based on any lore or anything else based within the universe... So take it with a pinch of salt if you will

The Elder Scrolls can foretell all possible events that have and to occur in the world of Nirn. The sheer amount of knowledge and information scars the eyes and shatters the mind of those carelessly open them without proper training and preparation. The actions of mortals has always been a source of entertainment for the Daedra and a source of forbearing for the Aedra. But one stood apart from its kin (pronouns are worthless to the Aedra/Daedra), instead of watching from on high with the Aedra or the Daedra merely meddling with the lives of mortals to survive the tedium of eternity, rather this one was compelled to the scrolls like a moth to a flame. It's boundless curiosity sought to live out the possible lives of all permutations and combinations of events that shape the world of Nirn. From Hero to Villian, this Daedric Prince is addicted to the experiences of the lives that alter the face of Nirn.

The plane of Oblivion that this Prince hails from is the forgotten realm of Teria, a garden-like world with blue skies and the stars of limitless possibilities. The Prince itself is rather elusive, as there are many forms within this plane of Oblivion, all of which are fragments of him and each fragment is as unique as the other. Each fragment has a unique mind, seeing the planes of oblivion, Nirn and all the cosmos differently (even slightly) to each and every other fragment. When the fragments are eventually drawn to the world of Nirn, they are bound by the threads of time and fate to specific Time threads that are tightly bundled , most importantly to points just before a major event within the timeline of Nirn. Generally they take the form of a lost prisoner, a faceless champion (Daggerfall), or other forms that are easily forgotten by history. Each fragment of the daedric prince is drawn to a particular possibility or permutation that could change the events that would take place. This includes races, genders, sixuality, beliefs, and so forth for each difference could have a possible outcome within the world of Nirn. Each fragment is drawn to different moral choices which inevitably carve new aspects to the face of Nirn (especially Tamriel).

Once the daedric fragment has completed the tasks and events of the time period it was drawn to, it returns back to Teria and archives itself and it's experiences within the world of Nirn back to the Daedric Prince himself. Collectively it has experienced the world of Nirn through the eyes of a mortal, which is both prized and shunned by both the Aedra and Daedra. Possibly why it is forgotten about in history, despite having possible connections to Akatosh and other daedra in his experience of time and change and existing outside of time, it is the aspect of envy and shame to the "Gods" of Nirn.

So, the daedric prince has been the Nerevarine which ended the immortal tribunal, it has been the hero of Cyrodiil and Daggarfall and it has been the Aegis against the World eater as the Dovahkiin. The Daedric prince has experienced these lives in all possible combinations and the threads of time and fate still continue on. The daedric prince has appeared in the world of Nirn 5 times to this point, each around the major events that have shaped the world of Nirn.

Where will our daedric prince appear next, we will have to look Elsewhere for the answer....

tl;dr:

The player is a portion of the Daedric prince who experiences the events of whatever game you have installed and your unique character is a possible permutation of the events that lay out the story and thus each and every ending is indeed canon. DONE