Why extra/additional bones don't work with @ animation pipeline?

Hi,

I'm using Unity 5 (but in Unity 4.X I have the same problem), and this is my situation. I have a Warrior mesh, and some animations (without any mesh) like Warrior@Run or Warrior@Sheathe, and I'm using the "Update reference clips" functionality. I have some extra bones, like the Sheathe or the Sword bone that I want to be animated. I use this pipeline because I will have near 100 animations, so import a FBX containing all the animations each time we create a new one seems not scalable to me. I'm explaining that because yes, if I select this extra bones in this "all in one" FBX, the animation works no problem.

I tried to select the extra bones in the import settings (Animations->Mask->Transform) in for all the @ animations, also I created a mask to do that, but none of this two make it work. I'm starting to think maybe is a Unity bug...

Any thoughts on this? Do you know another method?

I really appreciate any help you can provide