Kinda been there, done that, don't you think? What with Cole and Anders doing just that already. I'm more interested in something like a Mage (I guess he's not a Magister) who witnessed something so traumatising that it completely destroyed his desire to have anything to do with magic (or maybe he tried, but he has a psychological block). And that Mage lives in Tevinter, I mean, how do you stay away from magic in Tevinter? Maybe his quest line deals with Tranquility or something sinister like that.
No, we haven't been there and done that To be fair, you said you haven't read every page of the thread, but this has been (and Maker's Breath, I have no doubt will now be) argued before. The character envisioned by many who have posted is not a mage, or rogue in any shape or form. No magic, and dubious on the "roguing", because there is debate on whether Sebastian counts. Just a pure warrior, in armor smashing or defending from things. Your character concept is cool, in fact very much so, but as with (by the Ancestors) Dorian, because he is s mage, he doesn't count. Besides, according to Vivienne, his magic would be permanently stunted, like Qunari saarabas, without proper training. And I highly doubt he would be able to just live in Tevinter as proven by Dorian having to leave because the culture of magic first is so strong there. Unless the ritual killed everyone who knew he was a mage (remember magic manifests quite early), then someone would have found him to train him I would think.
Now if we got him and say the blacksmith lady KISA, then I'm down (sort of). But I would actually be much more interested in a character who's family didn't care that they were not a mage, and instead come up with rituals to essentially bind or coax a spirit into augmenting them, as apparently Tevinter mages use them for everything.