annoying immortal npc

I hope not because its makes me feel like oh I accidently hit you and you wont accept my yield now you will fight me until I start a new game or load an older save. Frustrating. It was always good when Morrowind let you defeat anything. E.G punch Vivec to death.

But if they have radiant AI they will need it to make shure a quest character does not get offed by bandits or something

As a old Morrowind player I would agree with at least protected radiant AI especially if important characters can now roam instead of staying still, if say any house members were to randomly be attacked for some dumbfonded reason and die via that ambush it would be really annoying and quest breaking.

I'd say only key MQ characters should be protected, and essentially no character should ever be marked essential.

Yes I agree with MQ charaters. Essential would be nostalgic-breaking. Again if people disagree they can always make their own mod to make them essential, post release.