There was no Barbie PoP line and has been no news of one. As for limiting extra accessories, look at Trap-Jaw. He has a belt, shoulder piece, 3 arm attachments, an extra arm AND an extra head. We only want 1 extra head.
I don't fully believe the "cost" answer as all their toys are made in China and they could make ONLY the rooted heads at their Barbie factory. As most the "majority" of fans...it was basically 50/50 without taking in account those who probably voted out of spite and will not be buying PoP no matter how it looks.
That's why they should do a rooted head boxset or just ship them in plastic baggies or something (like Gleek/Happy Meal toys). It doesn't matter how they're packaged as long as they make them.