Boo
 

Make it so you cant have kingdom mode on Main Island bc some ppl are getting on battle and then they get on kingdom so they cant get killed

They can't kill monsters either so it's not like they're cheating or gaining anything at all. It's only worse for them, since they can't kill for exp, or even get food.
Also it will kill RPing, say if (as an example, most liekely wouldnt happen)
Dustari Island wanted to attack the Samurai Island, and both the Forest Island and Pirate Island RPingly denied use of launching ships from or going through their waters, they have to go through main on K mode

but they can kill someone on battle and run and get on K so they cant be hurt and then wait until they can get on peaceful again and just make it so you Kigndom mode wears off in 30 minutes on main

Kinda rare that that would happen, and if the person could kill the guy, it's likely that after they killed them the first time the victim is most likely not going to have the stats, etc to come back and kill the aggressor.