[thxbb12]

It is odd, indeed, and totally unexpected - I was really going for m4/3 (also because of the wider lens gamma), but then I did the maths and found:

 

Nikon D5100 + Nikkor 12-24mm ƒ/4G DX AF-S = 1045g
Olympus E-M1+ Lumix G Vario 7-14mm ƒ/4 = 797g
Olympus E-M5 + Lumix G Vario 7-14mm ƒ/4 = 725g
Sony NEX-6 + Sony E 4/10-18mm OS = 568g
 
Nikon D5100 + Nikkor 18-70mm ƒ/3.5-4.5G ED DX AF-S = 950g
Olympus E-M1 + Zuiko 12-60mm ƒ/2.8-4 = 1072g
Olympus E-M5 + Zuiko 12-60mm ƒ/2.8-4 = 1000g
Sony NEX-6 + Zeiss Vario-Tessar T* E 16-70mm ƒ/4 = 651g
 
The latter combination is the one I most frequently use for landscapes, and with m4/3 is substantially equal in weigh (actually, 50/100g heavier). But even in the former combination there's a clear Sony advantage in weigh. How this happens, it's still a mystery to me, but in the end the Zuiko 12-60mm is heavy (in relative terms). The Zuiko 12-50mm is lighter, but it looks as it's optically bad from some reviews. The two Olympus look as they are the only m4/3 camera bodies whose quality is substantially equal to my D5100 (M5) or possibly superior (M1).
 

<div>Viewfinder all the way. 
 
</div>

 

Getting the 12-60 for MFT makes little sense. Why not getting the 12-40 f/2.8 instead? Sure, it's a bit shorter, but the IQ seems to pretty very good.

If I were you, this is the kit I'd consider:

 

Olympus 9-18 (155 g.)

Olympus 12-40 (380 g.)

Olympus 40-150 (or Pany 45-150) (190 g.)

 

The 9-18 is much smaller and lighter than the Panasonic 7-14 while accepting filters. It's slower, but in terms of IQ the difference doesn't seem to be that great.

 

Total weight: 1220 g. I think you'll be hard pressed to find something that weighs so little while being so small...