Let me say first off that I got my wiring panel from a RV. The RV had a 12V ground terminal ,and for "Every" 12volt light/circuit had a ground wire that was connected to this ground terminal. And most every hot wire had it's own fuse in the panel.
Do you guys think running all of the 12 volt grounds back to a grounding terminal is really needed ? Or would you see a problem in connecting several ground wires together ,, then running one larger ground wire back to the grounding terminal ?
And for that matter, running several power wire together also ? Automotive systems often connect several items together on the same ground /and or power wire.