I like the one code collection per character scheme (even if peeps create throw -away chars--which I am not a fan of) and even if the ships were very hard to kill they would be pilfered regularly--unless you put them near Nomad bases and the like. Perhaps Nomad b-ships killed in Iota with the mission near a base? (Haha--that would be fun). Other alternative would be to place npc b-ships on par in power to the Isis and have missions/spawns for the codes be right on top of them.