Ok, I can create character animations in blender and export them to the game without much trouble, but I run into problems as soon as I try to create involve an idle object mesh.
If I add a "NiStringExtraData -> Weapon" field to an Idle object, It attaches itself to the weapon bone in-game. When I try to attach the bone (using a ChildOf constraint) in blender, its rotation is completely wrong. I only get this issue in blender, in-game it works fine. The main problem is that the blender issue stops me from creating any animations using my idle object.
I only really want to create an animation like the vanilla Bethesda ones (e.g. painting, drinking from a mug) but due to the object rotations in blender and in-game not matching, any animations I make will be out of sync with their idle object. A good way to see what I mean is to try and get one of the default Bethesda animations into blender that uses an Idle Object. He animations itself works fine, but as soon as you parent the object to a bone on the armature, it doesn't line up like in-game.
Thankyou for any help I can get, I don't have a clue what to do next....
PS - I also found that the exact same problem can be triggered in blender when parenting a sword mesh to the weapon bone. The rotation of sword is all wrong compared to in-game, even though all the rotation and location values read 0 in the transformation properties window.