Its interesting to note that the 737 line underwent significant re-engineering about a decade ago. Assembly of body sections was moved from a system of alignment jigs to l@ser-guided, computer controlled jacks. One attribute of this system is that there are no tooling parts that cannot be loaded into shipping containers and moved to another factory. Most things are done from the (floor-mounted) jacks, so factories no longer require expensive overhead cranes. All that is needed is a flat concrete slab and something to keep the weather out. And the 737 line is still here in the Seattle area (more or less).
Granted, the 737 is the smallest and easiest airframe to implement this with. So the 777 will certainly uncover some major issues.
One thing I waited for, but never lasted long enough to see, was the possibility of all lines being assembled with a common set of 'robots' (computer controlled jacks). With a moving line (another innovation back then) and sufficiently flexible tooling, it would theoretically be possible to build all models on one line, making production scheduling much more efficient. A 747 could follow a 777, with 737s stuffed into the spaces in between.
