Agreed...depending on how he transitions from FB to BB, it may be hard for him to get up to speed in time to contribute much this season. Ideally, he'd just make the switch now and be done with FB, but not sure if that's possible.
But in any case, what the heck? This is basically a free player, probably well above the level of a walk-on, at a position where we could use another body. Even if he only is a peripheral backup, there's really no downside.