That's what Dragon Breaks are for, and Dragon Breaks are involved every single time someone ascends to godhood or otherwise messes with divinity (and KILLING THE WORLD EATER WHILE INSIDE SOVNGARDE definitely qualifies). What happened at Red Mountain?
This. This is how Kyne and Kynereth, Akatosh and Alduin, Shor and Shezzar, etc. are different gods. Indeed, Red Mountain too (although MK explained through picture-song what really happened).
And while I know that, for the most part, the theory that Talos was a Nord is the most widely accepted theory at this time, weren't there, earlier in the series, rumblings that both the Bretons and the Cyrodils made claims to Tiber Septim's origin, as well? Given what we know about his physical appearance (which is to say, nothing at all) he could even have been a Redguard... though I'm not aware of any in-game claims to that effect. His origin as an Elf of any kind is unlikely... but what was Zurin Arctus? And how does Hjalti Earlybeard fit in to all this? And did Vivec somehow get in on this action?
There are some texts that say he was a Breton. Or a Nord born of Bretons or something. Or even Atmoran. But the majority of the texts point to Breton. Hjalti Early-Beard is Tiber Septim who became (1/8th of) Talos.
What I'm saying is that, in the long run, the identity of the Dragonborn doesn't matter--only the fact of the Dragonborn.
Bingo. Talos was the same. The actions of the deity "Talos" were actually the actions of Hjalti, Zurin, and Wulf(forget the rest of his name).