The problem is that the orbs cannot act outside of their bargains. At best, they can call out to people, but not much more that that.

The other issue is that we can only retrieve an orb if the previous contract has been concluded- and in Bracia, that meant we stole the orb, and then spent some time putting up with the owner trying to kill us all to get it back, until she gave up.

[Private]

So while it's possible that stealing the orb and making a new bargain- or the death of the previous owner- are also possibilities, they're untested ones- and frankly, I don't think most of the crew would be comfortable with murder.