Blender armature/bones vs. empties
(really a comment)
I needed a "mechanical" rig (bicycle) rather than a character. I rigged in Blender with parts parented to bones. One item (front fork) is angled. Then exported/imported into Unity (via FBX) with generic rig. Unity animation always uses global axes for the bones. This means the front fork rotation doesn't work right.
I reconstructed the Blender rig using empties instead of bones - front fork is still angled. When exported/imported into Unity (via FBX), with generic rig, now all rotations work correctly around local axes of empties.