A few thoughts.So, as I asked Maine Sail, do you see this as a good foundation, or any other reason not to wire the system as shown in my last diagram?
You have the house batteries wired in parallel. I think this is a good approach. This makes the 2 batteries function as one and that should provide more useable energy and longer life for the batteries.
I would suggest a few modest changes.
Eliminate the positive feed from the charger to the start battery.
Eliminate the positive feed from the start battery to the house panel volt meter.
Add a SPST battery switch between the Start Battery and the Battery Select Switch
Fuse the Start battery with a battery terminal fuse at 250 amps.
Change the 1-2-both battery switch to a Blue Sea Dual Circuit Plus switch.
Add an ACR between the DC Positive busbar and the positive terminal on the start battery with appropriate fusing.
Add a battery terminal fuse on the house battery
Add a battery switch between the house battery and the positive bus bar.
I think that's it.