This idea was thrown out last year. I don't think it would work very well because then people would just draft purely BPA instead of constructing a team and I doubt everyone would be able to make all the necessary trades to acquire all the right pieces for a team. For instance, someone could draft 5 centers because they thought they were viewed as BPA when they picked, but then not end up being able to trade enough of those centers before the tournament actually starts; they could end up not having a PG or something. Where as if you just do the trades before the draft, everyone will still be constructing actual teams as the draft progresses, like usual.
In other words, I think it would overcomplicate things.