very interesting proposition on the UKGSER page
Never heard of any such solution.
The probs with the standard BMW brake pads is that they're too hard, last a lifetime and are after a while pretty useless because glazed. Worse, the less the brake power, the harder the rear brake is pressed, which could end up in overheating the drum.
Try to get some softer brake pads - even if they wear off quickly, but without luggage I'm able to lock the rear wheel on tarmac. IMHO no expensive solution necessary.
Only when we pause to wonder
do we go beyond the limits of our little lives.