What about 30-60 second logout time. If you move your character you'll have to start over. If you're bleeding you cant't logout untill the bleeding has stopped. You may force a logout but your character will stay ingame untill he has bleeded out or the bleeding has stopped on it self. It works in all MMORPG's. It will work for Day Z also.
Should anyway be a non-exploitable way to have several characters. So you can play with friends on one and have another that you play one your own with. This basically means that you can't have two characters on the same server.