Use case 1 seems to be a minor improvement over a video call on a decent monitor today, and this is assuming that the AR and other tech would advance hugely from where it is today, to actually be able to do realtime filming and rendering with high precision, perhaps even in 3D to get some real advantage.
Use case 2 seems more realistic, but will be limited by eye tracking precision, component idenficiaction precision, and occlusion issues. Input will also be an issue (choosing which tooltips to see).
Use case 3 seems worse than building things in VR, other than some fancy art installations. Why would I want a virtual object that I can't view from my own home? Also, interaction would be fantastically limited, making the whole thing disappointing.
Use case 4 suffers even worse from interaction issues, and it also seems like a downgrade from current technology, which allows me to play in huge virtual environments without even getting off my chair.