I'm sure you're aware but if not Alexander Frater wrote a book called "Beyond the Blue Horizon" in the 80's where he did exactly what you're describing (London to Australia using scheduled air routes of the 80's to recreate the Empire run). He could not make it to 2 or 3 locations because there was no air service to those places but other than that he did a good job of touching down at all points on the original route.

An exellent read!