Yeah I see no reason to do anything but a doppelganger of the Chief. Halo 1 and 2 did it, ODST did it (with the Rookie). It's not a big deal.
I'm actually bugs me a little bit (emphasis on little) that the multiplayer has been given a fictional context. It's like was said in the first episode of Red vs. Blue, when the two guys are talking about why they're there in the canyon. Well, they're there to fight each other over the flag. Over and over. Because. My reaction when I heard of the War Games simulations on the Infinity was, really? They tried to answer that "why are we here?" question?
It's not a big deal, but I kind of liked how detached and absurd multiplayer is. It's the wacky side of the game, it doesn't need a justification to exist.
I'm the opposite... simply because in my opinion, more fiction, is better than less fiction.