Would replacing his original voice file work(even though I have no idea how to that I would still like to know)? Is there even the remotest possibility that someone could make a mod for it?

Totally impossible. Characters with unique voice actors (Hadvar, Ralof, Vex, Delvin Mallory, Brynjolf, etc.) can't be added to the marriage "faction" via console because they have no dialogue options for marriage even if you are able to add them.

Switching voice actors between NPCs is also something that isn't, to the best of my knowledge, possible. Even if it were, it's like swapping out personalities, in which case I'd find someone else to shackle myself to.