If you are boondocking for that length of time, you will probably need more battery capacity than I do. I very rarely go more than a night or two before I can run the generator for an hour to recharge the batteries, or I am on the road and the alternator does it for me. I thought about adding some solar panels, but I am mostly in wooded camping areas, so the shading makes them not worth the money for me.
Unfortunately, you will have to fabricate a cage and hanger system no matter what you do, because the one that comes with the unit will never hold more than one battery. You can either buy a battery slide tray already put together and just make the hanger system yourself, or get slides and make the whole thing yourself like I did. Kwikee is the big manufacturer of pre-made battery trays and they come in about a dozen sizes. If you just want cargo slides, Delcity has a nice selection of them online.
Have fun in the boondocks! I have another seven or eight years before I have to think about what to do in retirement