I don't have a Canon G16, but you might find the Canon SL1 worth considering as a middle ground between the D810 and the P&Ses. Canon claims its the world's smallest and lightest APS-C DSLR. Canon's STM lenses are also pretty small and light.
D20: 12MP, 5.6 crop factor, 28-140mm eFL, 7.7 oz
G15: 12MP, 4.6 crop factor, 28-140mm eFL, 12.6 oz
SL1 body: 18MP, 1.6 crop factor, 14 oz
Lenses:
1) EF-S 10-18 IS STM F4.5-5.6: 8.5 oz, (eFL 16-28mm)
2) EF-S 18-55 IS STM F3.5-5.6: 7.2 oz, (eFL 28-88mm, kit lens)
3) EF-S 18-135 IS STM R3.5-5.6: 16.9 oz, (eFL 28-216mm)
4) EF-S 55-250 IS STM F4-5.6: 13.2 oz, (eFL 88-400mm)
Canon also has some pretty light short primes.
Body + kit lens (2) (28-88mm eFL): 23oz = 1.4lb
Body + lens 3 (28-216 eFL): 31oz = 1.9lb
Body + lenses 1+2 (16-88mm eFL): 30 oz =1.9lb
Body + lenses 1+3 (16-216mm eFL): 39oz = 2.5lb
Body + lenses 1+2+4 (16-400mm eFL): 43oz = 2.7lb
I have one--it basically halves the weight and takes up less pack space than my "standard" rig but is otherwise pretty similar in both capabilities and IQ.
http://www.usa.canon.com/cusa/consumer/products/cameras
Doug