I don't know if anyone has suggested this but it is much easier to implement and would have less of an impact on the "innocent" players. You could simply have regions where the player cannot log out, i.e. you cannot log out in areas where there is loot. The one major downside to this is that if you want to establish a base using a loot spawn then doing so would prove to be difficult. One possible way to fix this is to make it so you cannot log out around high end loot areas and/or medium loot areas.