I've never heard of breeding for weaker potency as it doesn't make commercial sense, but to clarify what most on here already know, brick or shwag or whatever you called it is 1. A beautiful bud and 2. Nauseating packing procedures.
I get so tired of people asking why you'd plant brick seed. As though there were some lost genus of the cannabis family that grows into a smelly, moldy mess of squished, black buds...
Finally remember that the brick is decarbed, old and beat and the buds still got us stoned. Take a bag of og kush, pour coca cola on it and miz in pebbles and dirt, press it in a vice, leave outside in the sun all summer, outside in the rain a few times, then let me know if I would want to plant seeds of the OG after smoking that. ;)