I probably just resolved it myself - On importing the standard UE4-SkeletalMesh into Blender I checked “Automatic Bone Orientation” since all the bones are orientated and translated pretty strangely when not checking that. However, if I don’t check it, adjust the bones and auto-weight them for a quick test everything seems to work fine upon importing it into the engine. I’ll try that out later with a “real setup” as it is now 5:30am here but I’m pretty sure (according to what I just tested) that that was the problem. I’ll edit this post as soon as I have tried it out.