How to create prefabs without breaking SketchUp file (.skp) link?

I have a SketchUp (.skp file) model that i import to Unity. Objects appear like 'nested' prefabs (see image) however there is no 'proper prefab' that i can tweak to make it act like 'instance'. So when i try to create prefab, SketchUp file link is broken and it doesn't recognise the .skp model updates/changes anymore (auto-refresh feature).



So, how can i create prefabs without breaking SketchUp file link? What should be my workflow? Am i thinking/doing something wrong?