Have you looked at the option of harvesting rain water from the awning?
Simple and easy ...it just needs to rain...and, in our case, it always rains when we're away. As said in a previous post, we can be self sufficient indefinitely with just a little bit of rain.
That's with the two standard tanks and only 150 of solar with one battery. I'd think with the extra capacity you're getting, that would be possible.
But then, our camping is very simple and I know we're not the standard to judge it on but it might be worth considering.