Even staff Senpai agrees with this. This is only an idea that be done! - The only way playes can do this is by warning other players! - By this people can make EXP generators and other people who are lazy or some other reason they cant make there own . - If a person does not warn the other players and that player gets killed the owner of the island must give him back all the stuff back and a fine off 1000 $ - Or to make it simple just make a plug in where if a player visits someones elses island there inventory is fully empty.
A flag to allow others to attack hostile mobs is a good idea, it can be annoying when you get harrased by a mob and keep taking damage because you can't kill it.
I think that the rule should be that you can be allowed to attack hostile mobs, or at least take no damage when on another island. My second idea would stop warps which are infested with mobs. Either that or Killaura works