I find it rather odd how when catastrophe strikes Nirn, a hero is always there to either mitigate or negate it completely. In Arena, when Emperor Septim was imprisoned in a prison dimension of some kind, a hero, came forth. And then disappears. I'm not so sure about Daggerfall, but I do know that he does indeed disappear, as well. Morrowind, the hero was born, imprisoned, saved Morrowind, and disappeared. And as the pattern goes, Born, Imprisoned, and most assuredly will disappear when the next game rolls around.
Firstly, I find it extremely plausible that this is an attempt at avoiding fan-anger, but at the same time, I'd much rather have a lore/Elder Scrolls-like explanation.
So, my standing theory is that maybe each hero is a divinely resurrected champion, maybe a soul-successor to an ancient hero such as Pelinor Whitestrake. It could honestly be any one of such possibly numerous saviors, but his is the first name that pops to mind, as his task was quite similar in type to things the Player, as a hero, does.
And I can really state that I am no expert of the "Chim" concept, but I did find this:
From the Ehlnofex: an ancient sigil connoting 'royalty', 'starlight', and 'high splendor'
So is it possible that the resurrected hero is the soul of a previous being that attained this "Chim"?
As always, I leave myself with more questions than answers.