Out of curiosity where is it implied that the veil dosen't exist outside of Thedas? Because that sounds like an extremly interesting concept and like this could mean that the "fade part" of Thedas was cut off and isolated so with it beign a contained environment if someone managed to enter it physically like the inquisitor it could be thecnically mapped out (at least sections of it that are physically connected to each other).
mgdkfgjksdjgskdfgj i will attempt to drag down some codexes when i've got the brainjuice for it because i feel like that was alluded to but i may also be talking out of my ass and confusing between the implication that the blight doesn't exist outside of thedas with the veil.
i do think that all the funky shit that happens out on the amaranthine ocean indicates TO ME that the veil doesn't exist outside of thedas. i did wonder if humans came to thedas specifically because the rest of the unveiled world was a hostile environment for them as well...
theoretically it could be mapped out anyway, i think! when you're in adamant, the fact that you have to travel all the way back to the veil tear in the courtyard seems to imply some kind of fixedness to the fade which could theoretically be mapped out. the physics of that is going to make my head hurt, though.