According to this post, it is not possible for UE4 to allow users to package tools …
https://answers.unrealengine.com/questions/141273/is-it-possible-to-import-audio-at-runtime.html
Since the EULA forbids the use of any of UE4’s editor tools to be reused in a product you would need to custom build your own importer.
The following links discuss possible solutions for this:
Import resources (textures and meshes) at runtime:
https://answers.unrealengine.com/questions/202627/import-ressource-at-runtime.html
Loading textures at runtime:
https://answers.unrealengine.com/questions/23440/loading-textures-at-runtime.html