I think you probably do still have someone from within step up for the game, if not as an interim or co-coordinator, at least take a bit more assertive role. I don't think at this point you really care if McElwain is torn two ways or not, it's his offense, he calls the plays and it's hard to imagine anyone stepping in with the limited practices they'll have and doing better than even a distracted McElwain would do. I do think you still have another party take on more responsibility since the concerns go beyond just the game and into recruiting and the like.
I think the whole situation does make the Houston Nutt possibility offer a few more advantages. For instance, it's hard to imagine Saban doesn't get on the phone with Nutt one way or the other, he's seen Alabama's offense and LSU's defense, there won't be many coaches out there that could offer more insight. Likewise, let's just pretend he is a possibility for the OC position (I'd have to add that struggling as a head coach does not automatically make someone a bad coach, period), now he offers a bit more because he knows LSU, he knows Alabama, and he knows a lot of the kids Alabama is recruiting. I'm not saying he should be the guy, but given the fact that Alabama won't have a new OC until after the BCSCG, he's someone that might be able to make a more seamless transition than most.