I’m not sure about a generic API for this. There are just too many ways to use components, and they all have different expectations around arguments & load timing.
For your use-case, would a theme/plugin-specific registry work? Like the mockup above for right-sidebar-blocks?
If not, providing some concrete examples might help us to work out exactly what kind of API is needed. All CDCK-maintained themes & plugins have been migrated to gjs, and this isn’t a problem we’ve run into (except for the specific cases like right-sidebar-blocks).