the other components of that light system are the bigger evils to combat. I can figure out where to tie off a battery pack, but a bulky midpoint connection & shoebox like light, nope. again, I'm speculating what id what based on provided photos.
The wires and connections are not evil. Every thing is out of the way. Nothing interferes with the attachment of other equipment such as panniers, tents, sleeping pads and sleeping bags. The tail light is as small as it needs to be and looks good.