I have been through this process myself for very similar reasons.
I went with the SL1 as it was relatively inexpensive and had full compatibility with my EF lenses. The ef-s 10-18 makes for good wide angle images in a lightweight, familiar (dslr) package. You could also attach your 17-40 for a normal zoom with some weather proofing. When not hiking I like to leave my 16-35 on the 5D2, and 70-200 on the SL1 for ease of use and flexibility. Lots of options. - In reality I have problems with de-centered 18-55 and 17-40 lenses, and the SL1 front focuses so bad I only use live view for focus - something I can manage for landscape etc. So, it has the potential to be a good choice.
Based on your preferred needs; Wide angle, lightweight, weatherproof, and low light capabilities, I think the Sony A7 series with the FE 16-35 is unbeatable. Everything else comes with a compromise -
Canon 6D + (AMAZING) 16-35 f4 = heavy(ish).
Bombproof Olympus has smallish sensor.
Fuji X / Sony A6300 not weather sealed wide angle lens. This, however probably not that big a problem. If I have to shoot in the rain I use a cover of some sort. Water spots on the lens are the biggest problem.
Good luck!
I think the problem with the A7 series is once you add FF lenses it's getting big and heavy, plus the extra battery packs don't help...
6D = 766g (with battery, CIPA 1090 shots)
Extra LP-E6 Batteries (1 @ 80g ea) to reach 2000 shots: 80g
16-35 f4 IS = 520g
24-70 f4 = 600g (add 70g for 24-105)
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1966g
A7rII - 625g (with battery, CIPA 290 shots with EVF)
Extra NP-FW50 batteries (6 @ 42g ea) to reach 2000 shots: 252g
FE 16-35 f4 - 518g
24-70 f4 - 426g (no 24-105 equiv. option)
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1821g
I'd assume with less flash than CIPA specifies and not too much reviewing 2500 shots would be more likely than 2000, although the A7 eats a lot more power if the EVF is on, so you need to be careful how you carry it to avoid proximity to your body enabling the EVF.
I struggle to see how saving 145g is worth all the money? The size difference is what, 10-15mm? (The main issue he had seemed to be with how far the lens stuck out.)
http://camerasize.com/compact/#380.367,624.393,ha,t
If the OP wants the Sony FF system then I'm not arguing, go for it, but I don't see that much of a size/weight advantage over a 6D. Oh and charging 6 battery packs when you get somewhere with electricity will be a lot less fun than charging one! (Set an alarm for every 3-4 hours during the night?)
Other comparisons with batteries:
Canon 760D - 565g (inc battery and card, CIPA 440 shots)
Extra LP-E17 batteries (45g ea, 4 off) to reach 2000 shots - 180g
10-18 f4 - 240g (16-29 equiv)
15 - 85 - 575g (24-136 equiv)
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1560g
Canon 100D - 407g (inc battery and card, CIPA 380 shots, old sensor though)
Extra LP-E12 batteries (35g, 5 off) to reach 2000 shots - 135g
10-18 f4 - 240g (16-29 equiv)
15 - 85 - 575g (24-136 equiv)
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1357g
GH4 - 560g (inc battery and card, CIPA 530 shots, varies with lens)
Extra DMW-BLF19 batteries (c, 77g ea, 3 off) to reach 2000 shots - 231g
7-14 f4 - 300g (14-28 equiv, add 234g for Oly f2.8)
12-35 f2.8 - 305g (24-70 equiv)
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1396g
X-Pro2 - 495g (with battery, CIPA 325 shots with OVF 75%, EVF 25%)
Extra NP-W126 batteries (c. 47g ea, 5 off) to reach 2000 shots - 235g
10-24 - 410g (15-36 equiv)
18-55 f2.8-4 - 310g (27-82.5 equiv)
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1450g
Sony A6300 - 403g (with battery and card, CIPA 350 shots)
Extra NP-FW50 batteries (42g ea, 5 off) to reach 2000 shots - 210g
16-70 f4 (=24-105 equiv, effectively longer if crop the 24MP down to 10-16MP) - 225g
10-18 f4 (=15-27 equiv) - 308g
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1146g
Nikon D3300 - 460g (inc battery and card, CIPA 460 shots)
Extra EN-EL14a batteries (c. 47g, 4 off) to reach 2000 shots - 188g
Tokina 11-16mm f2.8 - 440g (16-24 equiv)
16-80mm f/2.8-4E - 480g (24-120 equiv)
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1568g
Nikon D7200 - 764g (inc battery and card, CIPA 1110 shots)
Extra EN-EL15 batteries (88g, 1 off) to reach 2000 shots - 88g
Tokina 11-16mm f2.8 - 440g (16-24 equiv)
16-80mm f/2.8-4E - 480g (24-120 equiv)
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1772g
That makes a total of three systems on this page needing no more than 4 batteries, the lightest being the GH4. Ho hum... I guess the question is partly what do you want to compromise to save size and weight?
Actually the 760D with the 10-18 and Tamron 17-50mm f/2.8 (non VC; or the 17-40L at an extra 66g) might be an idea, at 1419g. It'll take your existing lenses too and the controls work in a similar way. Plus you can crop to 12MP and get 40% extra reach (so 50mm -> 70mm).
http://camerasize.com/compact/#328.293,597.424,ha,t
http://www.the-digital-picture.com/Reviews/Tamron-17-50mm-f-2.8-XR-Di-II-Lens-Review.aspx
BTW if people wonder why I'm spending some time on this, the answer is I'm considering what to do next for a holiday system, and the results are surprising me.