TL;DR What's the best (or any) method for dealing with animated "equipment" that can be used across multiple character skeletons (most likely in separate spine files)

The long version:

I've seen a few posts that are similar to what I'm asking, but either unanswered or not quite what I'm looking for. So, I thought I'd try and ask myself 🙂

Suppose we have a game where you can be 1 of 10-20 different characters. All of the characters will have a similar bone structures, but won't be exactly the same (a girl might have a few extra hair bones, and the robot humanoid will have extra stuff going on with his face). Now, these characters can all equip the same equipment and armor. The armor is mostly figured out already with skins. Since each character is the same "size", skins work for the armor. But since each character will have slightly different unique features that require different bones, I can't do everything with one spine file.
So far, it's not too complicated. However, here's the tricky part: Some of the equipment and armor is supposed to be animated as well....

So, imagine a steam punk gun thing. It has gears that are supposed to always turn. Or a piece of Chitin armor that has spider legs on it that still squirm around.
How do you have these other animated assets be "usable" by any of the 10-20 characters that you can be?
With 100's of pieces of armor and equipment (quite a few of them animated) and the fact that they're supposed to be usable by any of the playable characters that are their own skeletons... I'm simply at a loss of how to do that.

If there was some sort of "skeleton" attachment that could reference other spine files, that would be amazing. But I know that's not a feature.

Any and all help would be appreciated 🙂

Thanks!