Basically I'm trying to build into my mod a compatibility fix for cloaks of skyrim without actually having to include their nif in my mod

First of all im planning to unpack the bsa into my data folder. Then in the ck make a new cloak with their model then retexture it using a TextureSet.

Then, using GetFormFromFile() ill incorporate a check into my armour duplicate function, so that if the player is wearing one of the cloaks, the script adds my marble cloak instead

Considering that all I'm including are the textures, if the player has Cloaks of Skyrim installed there will be no problems. It's when somebody doesn't have it installed is where my worries lie. Even though the player will never see it, there will still be my marble cloak sitting in the mod somewhere, without a corresponding nif in the data folder.

Im sure this must throw up some errors somewhere. Will this cause a big problem?

- Hypno

Couldn't you designate this as an additional plugin only for users with Cloaks of Skyrim?

I'm not really familiar with how to add "compatibility patches", regarding master's and that so my suggestion is probably silly.