Using vra 8.12.2
you use a combination of content sources and a workflow.
Meaning create a script that creates for you the projects with all settings in assembler and then also in the service broker.
Have project defined with "global" cloud templates. That projects van be used as a content source in the service broker.
The content sources are then being used then in the content sharing policy. (Add the content source and not the item).
And if you later add a blueprint to that project the it will be added into the catalog for that project.
And later just add a