I would have zero problem if the Celtics offered him the full (pro-rated for this year) Bi-Annual. This is for several reasons:
1)The Celtics are already over the soft cap level, so the only players they can sign are with the BAE or minimum contracts. The history of released players we add in late Feb or March helping us pretty low, and really non-existent since 2008. So no point in saving the BAE to wait for someone next month.
2) The Celtics may be too near the hard-cap next off-season to offer the BAE to anyone, so it's now or never with that exception. (I don't completely subscribe to this belief completely, which is why I say "may." Many/most articles I've seen take it as fact, because they think next year's cap will be the same as this year's. I think it could rise substantially.)
3) While it's not my money, the BAE isn't that much, relative to other contracts. It would be a shade over $2 million next season, which would make him our 9th or 10th highest paid player. If he were able to come in and be our 4th big in the rotation, that would be quite valuable, and not the same expectation as him being a starter.
4) If he were able to give us more than 10 quality minutes a game, the BAE would be a bargain. Furthermore, we would have Early Bird rights in the 2014 offseason. If he were able to give us 15-20 minutes of quality play, we could potentially offer him enough to keep him here long-term. Alternatively, we could potentially get something for him in a sign-and-trade if we didn't want to keep him (because he didn't pan out) but someone else wanted to take the risk for 2014-2015. (Someone else likely will.)
5) If he has a stellar year, we're not keeping him beyond 2014, because he'll then sign a sizable contract somewhere else. But we'll clearly have gotten our money's worth.
Really, the downside is relatively low (a couple million dollars (again, not my money, I know) that we otherwise wouldn't have been able to spend) for a player who doesn't contribute that much. The upside ranges from useful rotation player to the center we've longed for since Perk got hurt.
NB: We'd probably have to wait until the beginning of March for the pro-rated number to fall a little bit more to fit both Oden and another March signee under the hard cap, such that Oden would be paid about $1.3 mil this season.