At my remote camp, I have one backup battery bank that runs on a 100w panel with a stone simple 20 amp PWM controller, with nothing special, and I just have to add water to the golf cart batteries once a year. Your idea will work, and I like solar for unattended charging. After reading your clarification, you probably could even go simpler than the 45amp Morningstar and the remote panel. You will be surprised how much more capacity you will have: starting with totally charged batteries and even having one panel during the day while you're there, too.
