How do you all determine which NPCs to mark as essential in your mods? The reason I ask is because I've started the first interior of what I hope will eventually be a very large dungeon mod. The first section is going to be a long tunnel running under one of Skyrim's mountain ranges, and in the tunnel will be various merchants, travelers, guards, etc. I want to make it feel relatively active. The tunnel will have passages which lead to other interiors which contain enemies, like one would expect from a dungeon.

Anyway, I'm not sure how to handle flagging the NPCs, if any, to be essential. They aren't going to be quest NPCs, but rather merchants standing by their goods, guards doing their thing, and random adventurers who are traveling through the tunnel. I can see having the non-merchants not being flagged as essential. Should a player choose to slaughter the NPCs, that's up to them, after all it is technically part of the dungeon. However, I am hung up on whether or not the merchants should be killable and respawned as well.

EDIT TO ADD: I should mention that the tunnel is meant to be a safe haven for the player. However, as I stated above, the player could still kill things should they feel so inclined.

Instead of essential, set them to protected. That means that if the player decides to attack or kill them then he can do so, however the NPCs set as "protected" are invulnerable to all non-player attacks. That way no nasties inside the cave can kill the merchants, and they will therefore only die if the player chooses to do so themselves.

Another thing you could consider is to make shop keepers killable and, after a certain amount of time, another NPC spawns to take over for them so there is someone to manage the store again. That would give the mod a certain "real-world" feel. An area (in this case a small underground city) with nothing but empty, looted shops would tend to make the player lose interest in going back again, no?

Just my thoughts.

@SomeWelshGuy - Thanks for that suggestion. My current thinking for nasties being around the tunnel was that there might be an occasional skeever showing up from the lower levels, or a wolf wandering in from outside, but nothing strong enough to kill any NPCs. However, I'm glad you brought the Protected flag to my attention. That certainly opens up some doors in terms of keeping the NPCs around should I decide to add events such as random bandit attacks or something similar.

@Kreij - Excellent idea! That would allow the tunnel residents to possibly evolve a bit as time goes by. In fact I could build upon that idea by having merchants decide to pack up and leave, and then later new ones show up and occupy the empty space.

This brings to light another issue which I've been debating and not yet reached a conclusion. Say I do go the route of allowing all of the NPCs be killed by the player, I am unsure what I should do for naming. The majority of friendly NPCs in Skyrim have unique names. I am wondering if I should instead use generic names, for example "Khajiit Merchant" or "Nord Blacksmith". I really don't like that approach, but I think it would be better than recycling seemingly unique names.

I'm not sure how to do it (or if it's even possible) but could you create a list of "available" names for an NPC and when the NPC respawned it could choose a new name (but leave the EditorID the same)?
If you had a maniac player who repeatedly killed everyone the names would eventually recycle, but it would at least give a semblance of "someone new".

I would say you cannot set names on npcs dynamically, but you could create a couple of them, make a few copies with different names, drop them in a formlist and then use the random function to respawn one or another.

That's certainly possible. However remember that players generally prefer to be able to relate to characters. If you have a couple of nice NPCs with a bit of unique dialogue and a story, then people are going to take to the mod a lot more than if you have 5 generic "Khajiit Merchants".

Thanks all for the input and ideas so far. You've given me some new things to consider doing instead of what I had in mind already.