You know what sucks? Building a house with your friend, spending hours on it, and then some other guy comes along and completely obliterates all your hard work, because they have access to your protector. I think you should be able to specifically add certain people to your protector to prevent griefers from striking. Although some might say, ''build on your own then, or why are they even your friends?'', Well It is great to incorporate other players ideas and contributions, and that way you might learn a thing or to. And a lot of people tend to take a drastic turn when they see objects that they would like to own, sitting right in front of them. Honestly, just by putting in a command in the protector to add specific people would definitely benefit the building community.
So, please consider this idea.