i think a "temple of elemental evil" style system would work with the proper variations
when a party member gets to 0 hp falls unconscious. then he can get up to -x hp without dying, where x is his constitution or what other similar stat they will use in the game. if the battle ends before he dies, he can be cured, but will still have a semi-permanent penalty due to injury, that can be healed either by a doctor or by the party's healer with the use of the highest level healing spell of the game (that means only at very late stages you can be "safe" from injuries).
if he drops to -x-1 hp, he dies and will have to be resurected, but that will require more than just casting a spell. since the magic system is based on souls, the resurection magic will require for one of the party members to send his own soul in the afterlife to retrieve the soul of the dead guy. that means a party member will have to solo brave a dungeon of increasing dificulty as the level of the deceased gets higher.
he can abbandon the attempt at any time and will have to wait a day before trying again, but if he fails he will have to be brought back along with the other guy by another party member. if the last member fails, then the game is over (of course you can save before trying the first time and load if you fail, unless they implement a no save hardcore mode and you play that). the time one can remain dead and resurectable would be as many days as his wisdom or intelligence and after that he's gone for good