In Skyrim, there′s a ghost in Old Hroldan who seems to believe that the Dragonborn is Hjalti Early-Beard. The way I see it, he′s confusing your "Lorkhan essence" for the one which Hjalti also possessed. Any disagreements? These might not be the best words to describe it, but it seems to me like another solid proof that the Last Dragonborn is Shezarrine.
Something else just jumped at me though, which I didn′t remember. He also mentions how the Blade Masters of Alcaire taught them how to fight. Doesn′t that kind of turn "Tiber Septim is a Breton" into "canon" instead of "heresy"? At least Breton-raised, even if Nord/Atmoran of blood (given his name).
Any thoughts?