Hi,
I recently noticed that Bounding Box could work with weight, so I made some attempts.
It turns out that the Auto button is greyed out when a bounding box is selected. I had to go through each vertice and manually select bones and assign weight. In addtion, the check boxes for Overlay and Selected are greyed out as well, I could check them when a mesh is selected and go back to the boundingbox but they do not show anything more. Is this an intentional design or did I miss something or I encountered some bugs? I thougt the process shold be identical to assign weight to meshes since the document did not mention anything special with bounding box in the Weight section.