Ever accidentally go over the hidden electronic boundaries supermarkets have on their carts that makes them lock up? Imagine that happening, only with exploding Imperials or prisoners.
How would you set the proper range? If something happens to your base ship and you can't get back, you blow up?
I think the potential for the Rebellion to figure out a way to blow up every Imperial officer throughout the galaxy by hacking the system, would outweigh the smaller risk of defections.