In this
thread daplunk and shadowchemosh share some resources on how to get started in the editor and concepts that are needed to get you into scripting.
The ability as you describe it will definitely need some scripting to modify a natural attack field value (wDieSize to be exact) after you bootstrap it. Over at the
github wiki for the community are some coding examples. If you look for the article on
Natural Attacks, you can get a list of the fields that are involved.