We have both solar and a generator, but don't have as high of an energy need as what you're describing. Our panel and MPPT charger was only around $700 when I bought it 12 years ago, and it's paid for itself a long time ago as far as I'm concerned. We only use the two battery positions that the coach came with. There's just not room for more, and we really don't need more based on our history.
Most of our essential daily draws can be met with the single solar panel (e.g. lights, charging a phone, running the TV/DVD player occasionally). We cook with gas, and the fridge is far more efficient on propane than electric. For everything else, we run the generator.
Why buy solar if you already have a generator? Some NPS and NFS campgrounds don't allow you to run a generator outside very restrictive hours. It also keeps the batteries topped off when our unit is in storage, and is a fallback for if the generator isn't running or we're out of fuel.