Yes, in that situation I fully understand the context of positional scarcity. We can easily pick up a good hitting first baseman, but the same is not true for a shortstop.
I suppose I was arguing that it doesn't matter if baez moves positions because we already have Castro, a shortstop we like (hopefully hes good again anyways). Or If Olt works out, we don't have to worry about moving Bryant to the OF because we already have a third baseman that we like. If the more valuable position is available, obviously you want the prospect to play at that spot.