well my plan for this is this.

main cable from battery to the rear, nothing joining in on to it..
2nd cable to the middle ( i plan to put my inverter somewhere in the middle ) to small junction box. ( for future ideas,,lol )
3rd cable running just to the front of the cab,, i was thinking about hooking my stereo and uhf in to the 2nd battery but i thought why? stereo wont be on
when relaxing camp as my Bluetooth speaker and tablet will do my tunes.. hand a handheld uhf for keeping an ear on the airwaves...
but in the cab are i will have all cig sockets to the aux battery and usb charge points. when i get one, a 27mhz cb will be installed up front too on the aux battery..

i know this involves 3 lots of cables through the car but if one fails, i dont lose everything...