Consistent Predictable Behavior when embedding layers

[gotjoshua]

Feature description

It would be great, if embedded layers could be a bit more reliable, and understandable.
I would like:

1. if i embed a "legendgroup" from another project, that the reference will be stable even if i rename the group in the source project
   1b. at least i would like an error stating that the group of "a given name" was not found in the embed source
2. if i embed a single layer, it maintains a link to the source layer (so that styling changes will propogate)
   2b. if not, at least i would like to be informed that i am importing (and the layer will be independent) not embedding

Additional context

I think in a way this is a bug, but it feels more gentle to ask for a feature improvement.
While investigating i noticed some "interesting" things about the data model when checking the project file and how the embedded groups and layers are dealt with at the data layer. For example, a legendgroup is referenced by name, and the visible layers are not referenced at all, but the unchecked ones are in a list of hidden layers.