If you use a skeleton that’s different to the UE4 mannequin (bone names alone are too less as the rotation comes from the animation and the boneroll matters in that case as well) then you have to go the “retarget for different skeleton” step. Make a skeleton with a rest pose that’s very close to the UE4 mannequin A-pose. Make sure you apply all scaling and rotation before you export and there is no warning or error at import (which is perfect possible from Blender or Maya). It’s really no big issue as you could still share that anim BP afterwards for your meshes (that share that different to UE4 but same to your other meshes skeleton). If you really would avoid the “retargetting to different” skeleton step and using Blender then probably it’s possible somehow if you get your Blender to boneroll around the Z axis instead of the Y axis somehow (not sure). In my opinion you’ve to put a lot of time into it for an issue that’s workarounded very quickly otherwise. I’ve used my own created meshes from Blender, Makehuman meshes from Blender and Manuel Lab meshes from Blender all work together well with various market-place anims built for the UE4 mannequin. In my opinion this “share one anim BP for everything” is a bit overrated anyway. Even if my male and female character may share the same skeleton it would really suck animating them with the same animations. I’m using animations that looks completely different… but all of them can make use of the marketplace anims if I like with “retargetting for different skeleton”. If the pose matches then this is a task of a few seconds.
I’ve tried both approaches, importing as different skeleton and as the same skeleton. The distortion happens when I set it to be the same skeleton. When I import it as a different skeleton it doesn’t let me share the animations at all, even though it automatically matches the bones (because same name and hierarchy).