When I'm traveling, I find motels to be the answer, even if I have to get up early or stay out late. If you're not fussy, you could spend half a year in motels for the cost of $10,000 in mods or upgrades to a stock vehicle, and you would be paying the motel costs over a space (probably) of years, rather than up front.
But, the lure of the perfect vehicle is out there, and I even started such a thread myself a few years ago. My eventual conclusion was that a Toyota Tacoma doublecab with a decent topper would be the best solution (for me.) They will take you pretty far down rough roads, allow you to move a lot of equipment in and out, and also sleep inside in some comfort with a blow-up mattress and a good sleeping bag (that will take you down to at least 0F.) The other good thing about this combo is that it is common as dirt, and unlikely to attract the eye of anyone interested in a high-value theft. You can get very secure toppers, though they're a little pricey, and combined with the invisibility factor, you're in good shape. (EDIT: When I say topper, I mean the low kind that do not extend above the car, but are in line with it; that will save you several miles per gallon. Also, if you find a topper with a roof-weight rating, you can stand on them to shoot over foreground clutter, although that's dangerous. If you fall off backwards, you'll land on the back of your neck.)
One thing I noticed in another post was a vehicle project with a vehicle that had advertising graphics on the side. That may well be necessary for that person's work, but I wouldn't recommend that, or any of the photo-related vanity plates that may tempt someone (SHTRBUG) -- it's really advertising for the equipment inside. I once spent ~70 consecutive days in a very good tent, and my eventual finding was that in the more extreme conditions, when you really need a GOOD tent, even a really good tent isn't as good as the inside of a camper.