I am a bit thick at times
But so what? Why shouldn't it?
I was not at all thinking about PowerPlay by the way, so your remarks took me by surprise.
I consider the Bounty Broker proposal to be a general gaming mechanic, independent from PP.
Of course it's a PP problem. Right now, you have to search for and then travel to a far away system to collect the bounty on an Underminer, which involves a bit of leg work. But if you could just zap someone anywhere and collect a reduced bounty, then of course people will be hunting just for Underminers and making a ton of loot per hour. The implications for PP would be severe and it would massively dissuade people from Undermining. That would hamper 99% of the fun of power play.
Collecting a "black market" bounty in the target's home system would just be a slap in the face, but not necessarily unrealistic.
I agree with the general idea of this and there is certainly an economic niche for it, but can never be "independent from PP" as long as bounties are issued for undermining. Therefore if it is implemented it should be balanced with the PP mechanic and the rewards for Undermining should be concurrently increased to cover bounty risks. Essentially these are hostile targets and shouldn't really be incurring a normal bounty anyway, but rather should be altering your reputation with that minor faction or power.