Boat: 2008 Formula 350 SS w/ DTS, AXIUS (Gen 1), Smartcraft, vesselview etc.

I recently had an issue related to batteries and while searching for the problem I was looking at the diagram for the battery control switches. The image below shows how they are (and were originally installed by Formula).

Based on the original setup I can't see any benefit to having two separate switches for Auxiliary and Battery Parallel. On the other hand there are several downsides. The big one being that if the port-start+house batteries (combined into a single bank) are run too low, I can't run the boat unless I have battery parallel on. The reason for this is that the helm with all the DTS/Axius stuff starts freaking out if the voltage is too low, and in this situation the (brand new) alternator doesn't put out enough power to run the engines, charge the batteries, and keep the auxiliary system at >12v to keep DTS/Axius happy. If I had all this instead wired to a simple battery selector switch then I could simply select the starboard (standalone) battery for running the auxiliary system. I can turn battery parallel on but I have already had major issues from running the boa with it on that I don't want to repeat. If none of this makes sense, check out the image below. I made a simple truth table that shows how I think a battery switch would be perfect for this.


For you visual learners (like myself), here's a professional mspaint mock up of how it would look with a single battery selector switch replacing the two separate switches. Notice that despite how the first image obscures it, there is a constant connection between 3 wires permanently connected together for port and another 3 wires permanently connected together for starboard, my design keeps that same setup.

You could accomplish the same thing as the single switch and leave he current switch setup alone just by taking out the middle connecting bar between the parallel/aux switches and running a jumper wire from the parallel switch to the connector bar on the windlass/aux breakers. So then you could run off either batt switch or both at the same time....and no need to hack up the panel.