Your requirement is very similar to ours. We decided to get a high-end 5th wheel along with lots of solar power - 1000w worth of panels and around 1000Ah of batteries. We will go with propane generator, along with two 40lb tanks and a spare tank.
The idea is to find where ever this trailer will fit that isn't resort-like, and travel around for places to hike. We won't need fully serviced sites. With this much solar power, we should be able to camp off the grid two weeks at a time. With careful water usage, holding tanks should last about two weeks as well. And if during those few occasions where I need more power (AC or heat), I can use the propane generator. Our trailer will be around 37ft, so we won't be able to fit ours into small camp grounds but at least this setup will give us more options to go remote.
Just like you, I am considering a dually 3500 series diesel pickup and possibly a 37ft DRV.
