As far as your 2500 miles per year thing...I think Boomer should come out west for a winter. You could leave him at my place and we could explore Utah, Death Valley, and Baja (3 different trips). We could avoid lifting tires! I'd love to go on a couple of your trips as well.
It's unfortunate about the gearing you need but at least your Dana 60 is a full floater, so you can still get home with a broken shaft.
I don't have experience in driving a camper van off road yet, so I can't really relate. My green van is much lighter and I don't notice much fade, even after bombing down a dirt road for 60 miles (at 55mph). I'm always aired down quite a bit: 15psi on all the faster roads, 9psi on the trails. My 35" tires soak up a lot when aired down. Anyhoo, I'm using the Fox shocks that Agile Off-Road valved and haven't touched them in 10,000 miles (2,500 of dirt). I'm a Fox fan (they've sponsored me in motocross for years).
I wish you could do the TTB Dana 50 conversion...it's so reliable and easy to maintain, but I get where you're coming from. I've owned 6 four wheel drive vans and the TTB is 10 times better than any conversion I've driven. I will be interested to compare our Falcons once we meet up for a trip!
Coil-overs will put a lot of stress on their mounting locations. The force isn't spread out like factory coil buckets. If you break a mount, you will most likely mess up an expensive shock and you'll need a welder to get back home. You're smart though, so I'm sure you will address that situation.
Judging by this thread I don't see shock maintenance being any problem for you! I wish I had your work ethic! It might be a pain in the butt to get the valving right at first. If I were you, I'd give Ramsey a call. He personally valves coil-overs and he owns a van similar to yours. I bet he can get you in the ballpark with the valving over the phone. He's very, very knowledgeable.
Here is his van. He is running Fox shocks as well (that he valved himself).