Looks like you will need plenty of coffee and a very early start on the day you decide to attack the wiring job.
Were you ever tempted to have master volume & master tone for the separate necks rather than run combined from the 4 pots to the 4 PUP's? Does it also have a 3 way switch to select between necks as well as the individual 3 way for each neck? Presume you are using stock PUP's too or are you looking to upgrade? To add coil splitting too might just be the tipping point to a lengthy stay in the mental asylum!