Animating for interchangeable model parts? I've been trying to figure this out for a while and haven't been sure on what to search in order to find an answer to it.

I am creating a game in Unity whereby the player will be able to equip individual armour pieces (like chest/legs/gloves/boots/weapon/offhand etc).

I know how to animate an entire model with an armature, but I'm unsure of how to animate model parts in separate model files.

Upon inspection of a few other games, I have seen a few with a separated 'armature' file that I assume handles all the animating for all model files, but I'm not sure whether this is the direction I need to go, and I'm not even sure how I'd go about doing that.

In addition to this, some model parts may have unique bones related to them (for example: a shirt with a tie, and another shirt without a tie), would I put these bones on a single armature even though other connected models parts would not be using these bones?

I assume there's a simple way of doing this, as it'd be very inefficient to do a hundred or so animations for each individual armour set (with having to apply transformations, weighting and vertex groups to all of them).

Could someone please point me in the right direction?
My first instinct is to use a single armature, and have different meshes with an armature modifier pointing to the same armature.  In simple cases you could instead parent the mesh to one bone in the armature.  In more complicated cases you can use the armature modifier and vertex groups with weights to have the mesh modified by the appropriate subset of bones.

How exactly that translates to Unity, I am not sure.