If I were to release a mod that supported content from the DLC (e.g. changes weapons that only appear in the addons), will it cause problems for users who don't have the particular DLC?

Or will the unused weapons just lie happily dormant and ignored?

If you have DLC records in your mod, it would have the particular DLC as master. If the user doesn't have it, the game won't load.

From what I gather they will be unable to use the mod you've created. If you do release the mod just make sure you put in the description that it may or may not work if the downloader doesn't have the DLC's you used to create your mod.

That said, don't let the possibility of others not having the DLC's in question stop you from creating the mod and releasing it.

+1

Most people have the DLCs, and those that don't will miss out!

I think most everyone has the DLCs by now. If you are really concerned about it don't make it reliant on all of them or MZ. That would be my take on it.

Yeah makes sense.
What if you were to add a weapon with the same name and ID as the one in the DLC, without adding the DLC as a master.
Would the DLC .esm allow it to work as an overwrite?

I disagree. Many people who own Fallout don't own any DLC, and even more don't own ALL the DLC.

That is why many mods are released where the main esp/esm only requires the default game, and then release one or more optional patches that support the DLC.

Remember the XX in the FormIDs which represent the load order? So no. Many mods share the same FormIds, so thats why the first two numbers always change.

Thanks for the info everyone.
It looks like there is no worming out of releasing individual patches for the DLC if you want to make it accessible to all.

The reason I ask is that I have been tweaking and twisting my own game (with many of your good selves excellent assistance) to the point where I feel I'm about done. I have only been making minor adjustments over the last few months.
My game looks and shoots (my initial emphasis was on ballistics and damage, though it seems to have grown far beyond that) about as good as I always hoped it would and after going through the main game and most of the DLC (just Zeta and Lookout left) I am wondering if its time to put it on the shelf, and have a go at something else.
Still, I have put a lot (far too many actually) of hours into the darn thing, I am actually a bit hesitant to just dump it.
So I am thinking to maybe describe what I have, and see if anyone might be interested in having me upload it.

I probably would have done it a while ago, but banging the thing into shape for general release (readme's, getting the blessing of authors for all the bits and bobs, making sure that all the bits are in the right place, etc, etc) is a bloody daunting load of work in itself.
Tons of respect for all who have already released major mods. I don't think most users realize what an astounding heap of work it really is!