How hard would wiring like this be?

[cmdcheshire]

I am thinking of pulling the trigger on a Jazzmaster IV but i havent done much electronics stuff before and was wondering if a setup like this is extremely difficult : http://johnkvintageguitars.homestead.com/Jazzmaster-Bass.html

 

[AutoBat]

The wiring for those options is more on the complex end, although if you simplify it into sections it's not too terrible.

The nice thing about his page is that it shows pics of how he wires them up.
The components I see:
split/norm/reverse
series/parallel
2 band EQ
volume/tone

A good space-saver would be a rear mounted 9v battery, it looks like the Warmoth Jazzmaster IV bodies aren't routed as much as John K's. The upside to the battery route is that you wouldn't need to remove the pickguard when it comes time to change it out (about once a year, maybe less if you play a lot or forget to remove the cable from the jack often).
As of this post there is only one body in the showcase. Here is how it is routed:

If this is the path that you're thinking about going I would call in the order and be sure to ask if the additional routing is possible, much more like how the Jazzmaster guitar is done.
Jazzmaster guitar body for reference: