I quite like these ideas, especially the handover time as well as the cop requirement - You could even go a step further and involve vehicles for items that are of highest value - This would complicate things since you are not only more noticeable, but you're also a much bigger target for those that are hunting you. Not to mention that you'd also be limited (speed and mobility wise) which would present a great challenge for those who seek to acquire items of utmost value.