Modular characters are really the way to go as common assets like boots can easily be shared but it’s how the assets are set up as to what is require by the import process that determines if it will work or not.
Assuming that the first time you import the base character all goes well Unreal will sort the assets into a couple of different packages.
- The skeleton will be extracted as a stand alone asset which you will target future characters as to using a single SK asset for further components.
- The mesh is extracted as stand alone but will contain the hierarchy data as part of the added weight table that matches the naming convention as part of the SK hierarchy so when used in combination as a component both match as part of the complete package.
The key is both assets “have” to contain the same joint information even if the joints do not influence the mesh as to deformation requirement so even if you say export the boots using the same skeleton the the weight table of the mesh does not contain the complete set of joins as part of the table, even if you exported the same skeleton at the same time, you will get errors