When you import fbx into blender, the bones are completely screwed up
but you CANT modify them. What i did, its create a duplicate copy of the screwed up rig, wrote a script so that rig had “copy rotation/location” to all the bones in the fbx deform rig, and then rigged the copied rig so it was sane. By editing the control rig, the deform rig modifies and then you can animate it just fine. Is just really annoying.