So I'm experimenting with a large worldspace that expands the worldspace from an ESM. Essentially, I want to modify some small parts of the ESM with another ESM. I hear that TES4Gecko can do something like this with "Move Worldspaces"?

But I don't exactly understand what this does. Does it enable the ESM to modify the worldspaces, or does it actually alter the main ESM permanently?

Like, if I use Move Worldspaces from my ESM on Oblivion.ESM, would that permanently overwrite Oblivion.ESM?

Move Worldspaces doesn't actually move worldspaces, it just does something to the worldspace's ID so that its LOD shows up regardless of load order.

you should be able to modify an esm with another esm without the help of any external tool. unless i'm completely misunderstanding you.

I'd heard that modifying one ESM's worldspace with another ESM can cause major issues; even so much as placing a door. I suppose I should do Move Worldspaces just in case then, since it only edits the ID.

I basically have one ESM with the main world for my mod, and another ESM will act as an expansion, adding another segment of forested area to the east of the main ESM's worldspace.

You can't modify interior cells or exterior worldspaces in an ESM with another ESM. You have to use an ESP to do that or you'll have chunks of landscape missing from lots of places in the game.

why not just make it one big esm?

But wouldn't Move Worldspace make the ESM's landscapes behave like the main ESM's landscape, since it's "injected" into the main ESM?

@Nerevar: It's mostly for theory right now, as a particular project I have in mind may call for it.



EDIT: Here's something I might try that I saw from the De-Isolation tutorial. ESP mastering would allow an ESP to use another ESP as a master; as though it were an ESM. This would mean that mods could be made for the ESP, right?
If so, would it be possible to include an unchanged ESP that uses my mod's ESP(s) as masters, so that people can mod it easily without having to ESP-master it themselves? (using that unchanged ESP as a base)

I highly recommend that you use only the one ESM(#1) and your esp as only an modification . If you decide you want to make another ESM(#2), it should be ONLY your new data(meshes,textures, misc, etc), that does not in anyway modify the ESM(#1); and if choosing this method, you would use a new esp for your new modifications for the two ESM's loaded as its masters. Any deviation of the two methods above I find either mod breaking, or too confusing for players that can potentially give you lots of headaches. Trust me, do it the easy way.

Doesn't matter. The game would treat it the same way. Your ESM that alters the other ESM would still be editing the worldspace records.

You either need to merge everything into a single ESM and go from there, or use de-isolated ESPs as you're discovering. You just need to remember to flip the ESM flag back off before loading the game or you'll run into the same problem.