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The first thing I'd do is install a Victron BMV-712. This will give you all of the information you need on usage to make your other decisions. The BMV-712 as you probably know is bluetooth so you can leave the monitor next to the house batteries and monitor it with your phone or laptop.
Do you plan on solar panels or using your generator to charge your batteries when you're boondocking?
To charge the house batteries when driving you can use a battery to battery charger, either a Victron Orion or a Sterling.
Some of the FT guys have put together really nice systems. Search for Roger Engdahl's or Oscar's posts on the FT forum.