I was looking for a traditional plugin system with various objects like scene, mesh,etc... and behaviours to add to mesh plugins for rotate or whatever.
Like the old Babylon3D plugin that was abandoned and dropped support, i uploaded it here with the dev permission:
It uses the old 2.6v of Babylon.
Here some videos i did time ago:
Maybe looking the plugin you or somebody can see the amount of work, organization,etc... to get a first aproach or get an idea how to do.