Personally, I don't really understand your idea, or how it would be done. Then again, I don't know what the thief guild membership really does for anyone. All I know about it is you pay a ton of cash so your name gets listed somewhere. Whoopie.

BTW, isn't the bounty office useable by anyone? I've never tried to actually post a bounty or cash one in, but non assassins seem able to see who bounties are out on, how much, etc, etc.