Yup. The common sense in this thread sometimes comes through in bits and pieces.
For our European expert, it should be pointed out that sometimes a team will do things like run a "three guard set" or run a big lineup. This basically means that in real life teams aren't always lined up with a typical PG-SG-SF-PF-C set. Sure Scottie Pippen could handle the ball well and bring it up court and shoot from downtown, but he could also crash the boards with the big guys. He wasn't going to guard Charles Barkely too often, but he could switch over to him in a pinch. John Paxson could not guard Charles Barkley. (Sorry if I'm making you have to research the history of arguably the greatest dynasty the NBA has had, with apologies to the Celtics fans of old.)
BB doesn't have the option of running any sort of lineup other than one of each position. BB doesn't have players switching over to guard players at other positions. We're a little limited here. I assume in a few years the developers will be so advanced that they'll burn the game engine and just have robots that they programmed running the games in real time that we can watch streaming on our 3D computer that will flash holographic highlights from the PDAs we'll all have wired in our heads.
But in the meantime, we need a way to train versatile players without having to put them out of position or water down the training while training at least 2 or 3 players at the same time.
Don't ask what sort of Chunks they are, you probably don't want to know. Blowing Chunks since Season 4!