I've been looking around for something like that, and it - to me - came down to either a Toyota 4Runner or BMW X3 (too small for your purpose) or BMW X5.
The 4Runner (2010 or later is all I've seen so far) has *a lot* of cargo space when all the seats are folded down, and the cargo space floor is flat and level. If you cover the cargo area with "shower pan liner" (a very thick urethane membrane), it would protect the flooring, while making it easier to slide gear in from the back.
The 4Runner has a decent amount of "motor" - nothing spectacular, but enough to get you there. Has lots of ground clearance, and gets great reviews for off-roading etc. Decent fuel mileage for it's weight and size as well. The on-road behavior is supposedly soft, vague and with lots of body roll in turns etc.
The "Track" version has a "pull-out" cargo floor, which allows you to pull out the "shelf", load your gear, and then push everything back into the car. It is an option on the other models. This pull-out would be great for on-site gearing up - maybe a bit low, but at least an option.
The 4Runner does not have any tie-down points in the cargo area. Don't know if any can be mounted. It might be possible to mount rails on the cargo area floor, but probably only on the rear-most area.
The Beemer is big and expensive, but a great driver - if you enjoy driving as opposed to just being "transported" from place to place
It has lots of cargo space with built-in rails for tie-down points. The dealer couldn't give me a load rating for those however. The cargo area floor is flat and horizontal.
Lots of ground clearance and powerful and not too "thirsty" a motor.
I looked at the Honda Pilot, and the cargo area floor slopes up and didn't seem that it'd be as easy to load as the other two. Didn't care for the fuel mileage and driving either.
The Honda Ridgeline might be a good option: Truck like bed (a bit small maybe) but car/SUV like interior and a suspension that's a compromise between truck and SUV. Handled ok, and was nice enough to drive. Steering wheel is tilt only, but the Limited version is nicely equipped. Gas mileage is poor in this day and age.
I read up on the Mazda CX9, and it is supposed to be a fun driver, with lots of space for the $$. Haven't seen it "in person" though, so can't speak to the cargo area.
The Honda Elements would seem like an ideal candidate, except for the measly GVWR. IIRC you should load more than ~800 lbs into it (passengers and cargo combined), although that may have changed since I looked. I've rented a few, and they're econo box drivers, but they'll get you there. Don't know about ground clearance.
Hope this help. I'd be interested to hear what you find.