I was thinking of the following simple goals and related architecture similar to this personal repository:
Store multiple artifact bundles in an "artifact-bundles" directory
For each artifact bundle, provide the sources of Build Plans and Plan Scripts in a clear text format embedding description, in an dedicated "src/" directory. As a consequence, potential cloners don't have to install/extract the artifacts to view their content. Specially if they don't have an Image Streamer yet !
The sources can be automatically generated by a script like this one
Additional documentation and collateral can be provided in a "docs" directory
A consistent naming scheme should be used for each objects
Then, as a shift is happening from Guestfish Plan Scripts working in the root partition toward "UEFI" Plan Scripts using the UEFI partition for storing before next reboot and deployment, a decision should be taken whether we use :
one branch per IS version (4.20, 5.0, 5.0+...) as done in other Image Streamer repos
2 branches: "legacy" Plan Scripts and "UEFI" Plan Scripts
Only the master branch
My take is to go with the last option with a -EFI string in each artifact/BuildPlan/PlanScript when those are refering to the new EFI deployment method. Maintaining several branches leads to a proliferation of objects containing "almost" the same content, hence confusing potential cloners.