As far as I can tell, there is no technical reason why the B-Bone segment thickness scaling can't be separated into two axes. The only downside is the increase in complexity of the B-Bone settings, but this is inevitable due to the increase in flexibility. Updating the file is somewhat complicated though, because F-Curves and drivers have to be duplicated and updated to the new names. Reviewers: campbellbarton Subscribers: icappiello, jpbouza Differential Revision: https://developer.blender.org/D4716