what is the final dpi for the final large format size? you can significantly reduce the amount pixels.
As I figured it, at 8ft long for you to have 40,000 pixels wide it would have to be a depth of 400+ dpi.
At 300 dpi with 96 inches you reduce that to less than 29000 pixels wide.
That being said the human eye can only really percieve around 96 dpi, so if you halved the dpi to 150 the size reduces further to a respectable 14400, which is much more manageable.
Even at 200 dpi you would be at a more manageable 19200 pixels by 10800
Just thinking about computation time and the like. As far as particular methods and such, you sound like you have a solid methodology that you want to follow.
Could you do some areas of interest and post those? I am very interested in seeing parts of this behemoth