Still depends on what you want, need, to achieve ... and I'd add ... how experienced you may be using a M rangefinder (I'm assuming you are).
The end result/use would dictate a lot of the choice I would think. Nothing cheeses me off more than getting home and wishing I had taken a defining shot with a better camera.
For sheer IQ, dynamic range in bright conditions, and crop-ability, the H4D/40 wins hands down ... and as you probably know, less critical snaps at ISO 1600 are excellent when exposed properly. Whether I'd take my Hassey on a trip like that would depend completely on what the images would be used for.
Traveling with a H is easier than most would think if it's set-up correctly (hand-strap & wide, bouncy elastic shoulder strap), I use the viewfinder and body cap so I can remove the viewfinder to pack more compactly. When I travel with the H4D, I usually take the 50, 100 and 1.7X, which both take the same polarizer ... and the M9, 28/2 and a 50mm ... or 21/1.4 and a 35/1.4.
I haven't traveled with a 35mm type DSLR for over a decade.
Were it me, I'd use my M9 for the candids, markets, and it would depend on the nature of the photo-shoot whether it could work there. However, I'd include a fast M50mm of any flavor.
The X100 is so small, it's a no brainer to take along ... but as far as IQ it isn't a back-up to the H4 or M9.
It's always a dilemma choosing between size/weight verses end result ... which is why I still maintain two M9s, and they are the main travel cameras for most trips: Two M9s, 21, 28, 50, 90 in one small shoulder case. I can ever remember wishing afterwards that I had used a different camera as far as IQ is concerned.
-Marc
P/S ... the M stuff fits inside even the smallest Hotel safe : -)