1) I think most of us that travel with our gear don't worry about weight.
2) I actually think that most of us don't try to service on the road. Instead, we bring one extra 1st, one extra 2nd, and a couple of hoses. We already have a backup computer.
3) If you're going to be gone long enough or on a rough enough trip that you almost expect a failure (crew mishandling? Who knows?), then the original considerations in your OP apply:
a) reliable
b) familiar designs (bring a service kit +/- spare parts for a technician)
c) easily serviced without lots of specialty tools
"Longer service interval" regs don't help. If they're getting heavily used, general quality is maybe the bigger factor.
Some might argue that a sealed first stage design might help you here.
Finally, learn how to open and clean out your second stage, and replace the diaphragm and cover without a leak. A heavily used reg will accumulate sand and the occasional piece of junk that suddenly makes it breathe wet. You don't want that easily fixable problem to be a deal breaker for a trip. You don't want someone else doing that simple fix on
your reg.
And apologies to @BoltSnap , if you're really in the middle of nowhere and don't do DIY service, I might be less inclined to bring my more complex Atomic second stages, because there are a couple of critical tiny parts. I might choose a more standard design second stage, but of similarly high quality.