One of benefit training OD is that it also trains ID, but don't you think it is difficult to reach 10 in OD for a tall PF or even C ?
First of all it is difficult to find C from the draft high OD. In this case he might have 1 in all other "small" skills. And other thing - to get to lvl 10 you'll need nearly a full season, are you sure to have enough time to train other, primery skills for a Big man ?