Read the whole discussion , there's plenty of information from me , it's better to try ... than do nothing. Last session there was a 10 minute cooldown on relog what was shortened to 3 minutes by most players. My suggestion is to make a 3 minute cooldown for those who do pvp , i don't see anyone putting much effort in bypassing that like it was last session.
It is irrelevant whether is it 10 or 3 minutes, it WILL be bypassed and achieve nothing. Only real difference between "pvp cooldown" and it sitting there for anyone is the lesser amount of people being bothered with that.
But for people that want to do it this is still the same minor setback, that can be fixed by very minor amount of spoofing.
The number one problem of internet (and not just gaming), always was and will be the identification of person.
So the effort to break any limitation is always very little (especially compared to creating those limitations).
Keep in mind that if you log out of one character, even in combat, only prevention from letting you log back to the server would be tracking user by data (easily spoofed, no matter how complex is it), or by login. Since the game does not charge you anything for creating an account, there is no way that can ever work (though granting relevant bonus to characters on single account could discourage people from abusing this).