In order to create a quick patch for a mod item to work with a custom race, here is a method i have used for a couple other mods.. Including the ones posted by ikahurula.

Go to the FCS and open it, create a new mod (button on the right hand side) and name it some like "skeleton KLR-M upgrade module patch".

After that, make sure you enable the newly created mod by having the "ACTIVE" on the right hand of its name.

Now open said mod in FCS, and on the top click "merge mod" and find the mod folder. It will be in [workshop -> content -> 233860 -> 15933229562].

Find the .mod file and mark it, then open it.

This will simply merge the changes of the mod, creating a dependency and allowing you to make edits based on said mod. Do the same for any skeleton mod you want to add them for, as in merge the changes.

Now that this is done, you will have a window with a bunch of categories, one being "races", open that and it will have "groups" in it, click that and the right hand side will have "Hive, Human, Shek, Skeleton, Southern Hive" based on what races are ingame and playable.

What you want is to first of all, ensure the races you are adding as being able to equip said item are actually here, and for mods that add hats or armor, the correct slot is actually useable (dont worry about this if the upgrade goes into a belt slot).

Now.. At the top click on "Changes" and find each of the upgrade modules in the list that opens. Double click them to open them up.

On the right hand side, check if it is using a "races exclude" or "races" option. What they do is simple: Races means ONLY those of the given race can use it, while Races Exclude makes so the races listed can NOT use it. What you want is to check if it excludes the organic races, or marks the skeletons as able to equip them.

If it excludes organic races, you can delete your new mod and just go back ingame without doing a thing.

If it lists races, you simply switch the drop down menu at the top to "races" and click add, and add the new skeletons to the list, save, load your new mod after the skeletons and upgrade module mod, and enjoy upgrading the new skeletons.

I hope this was clear, and not too long a read.. And somewhat helpful.