Right now my Speed Concept is set up like this:

Two SW-R671 shifters
SM-EW90 3-port junction box A
JC-41 junction box B
DN-110 battery

This is all set up "normally". What I would like to do is

Two SW-R671 shifters, one set up to shift the rear derailleur, one not wired as a dummy
Two Shimano ST-6871 brake lever/shifters
SM-EW90 5-port junction box A
JC-41 junction box B
DN-110 battery

I would like to wire the shifters and the battery to the 5 port junction box, run a single wire from the 5 port junction box to junction box B, and then wire junction box B to the derailleurs. I want to hide the battery in my left aero extension.

Will this work?