Ai allows you to isolate a single path within document structure, but it only applies to groups. If you want to isolate a part of the compound path/shape — you won't be able to do it.
I fully understand that this requires Ai to decide what to do with art that is created at this isolation level, especially not ordinary paths: type, mesh, brushes... But this can be checked, both creation and pasting and dragging.
Speaking of compound shapes it would also mean that the boolean result will change.
Still, a very welcome feature.