Would a route where I fly direct to Shanghai, and back transfering via a third country be valid?

You're absolutely right because the visa free transit rules clearly says: Only the immediate airports before and after your Chinese destination matter and they have to be in different countries!

In other words, the immediate airports to your Chinese destination in your case are Paris and Amsterdam, i.e. the cities in two different countries that make your itinerary definitively eligible for 144 hour visa free transit.

Amsterdam - Shanghai - Paris - Amsterdam

Is the right choice for this visa free transit option.

This is what I'm hoping will work also!

Sydney - Taiwan (4 hours) - Shanghai (60 hours) - Sydney

It will work perfectly, don't worry.