Hello,
is it corect that during your Build creation you create additional structures, partly with files, in your local Sandbox area, and that you are using the function "AddMember" to introduce them into your server-located project?
In this case you don't have any chance to create empty subprojects, because the AddMember Wizard requires at least one artifact in the directory you want to add as subproject. (AddMember)
The creation of empty subprojects is limited to the function "CreateSubproject". If the structure is already the same, it should be possible to use a CLI-command "si createsubproject --createsubprojects --project=/Projects/test/project.pj --changePackageId=:none --hostname=SERVER --port=PORT -F STRUCTURE.txt"
with a template structure in the text file STRUCTURE.txt
After your build you can add all created files and you will have empty structures with only two commands.
Nice try
Klaus