I agree that he could play the 2 or the 3. Might even be able to play the 4 in a really, really small lineup if he is that good of a rebounder.
Too many fans get caught up in differences in the 2/3 spots IMO. Probably due to the NBA game coming to town, where there is a difference. But with the offense most college teams run, including OU, there is no difference. The 2 and 3 spots (and really the 1 spot after the initial pass) all do the exact same things in OU's offense. So at the end of the day, it doesn't really matter.
If we land Mr. Koulechov, my preference would be to start him at the 3 over Odomes. But you are right, if McGusty leaves the game it's entirely possible to slide Koulechov down to the 2 and bring in Odomes for the 3. Again though, as to what they will do on offense, there is no difference. Any difference has more to do with the defensive end more than anything.