One thing I honestly feel is a big dampening on game immersion, is the ability to simply load/reload saves immediately after being killed. Its also frustrating if you forget to save before a certain point, you need to reload a save that could have you replaying or repeating certain events to catch up to the point you were killed from. One mod I feel would complete this game, is an option to Respawn at a nearby inn or maybe crossroad fast travel point, with the game world left in tact and your health in a lower state. Another feature could be that if you had a companion, you would remain in a bleedout state while your companion fights. It may not be do-able at all in Witcher 3, but if anyone was considering this, it would definitely be a great game changer.