Wow, this looks fantastic! ROS Index is well overdue for a facelift. I think the core / non-core distinction is helpful. It might also be helpful to filter out packages that are exclusively message definitions.
I might push back a bit and ask you if we were to extend package.xml, what would you like to see? I’ve been saying for quite some time that we need a mechanisms for tagging package types (e.g. control, planning, hardware drivers, hardware type, etc).