I am going to be useless and suggest the x-e1 or xpro1. (i know this is possibly making the decision harder but......)
I am also going on a trip this summer (Switzerland, Germany, France, Czech Republic), and much like you I have 5D3, 70-200isII, 24-702.8II, 16-35II, 100-400is, zeiss 50, 85, 40, and a few older cheap zooms, plus all my film equipment, flashes, accessories, you get the picture......
I decided to buy the X-E1. I have done a fair bit of shooting/testing with it and the image quality is suburb! (14, 18, 35, 60 lenses)
I feel like this is a ideal travel camera because of its small un-intruding size and its minimal weight. I feel like the 5d3 70-200 combo weights more then my whole Fuji kit (I am almost certainly wrong but it feels this way!!!). I will say I lean more towards landscape and city-scape where the Fuji's major flaw is less of an issue. As you may have read elsewhere the focusing can be slow and under certain circumstances hunt a fair bit. I am not a major street shooter so the magnitude of this drawback is unknown to me, but for the little bit I do it has worked.
I also should mention I reached this decision as I will NOT have somewhere safe to leave my camera, as such I will have it with me 24-7 for 1 month. I was not so afraid of the theft of my canon gear as I was concerned with the weight after a week or two (begin to hate carrying it and as resentment grows stop taking pictures all together, which defeats the one of the reasons I am going
). for you this may not be as large of an issue, either with weight or safe keeping.
I am also traveling with laptop tons of filters, tripod, accessories as such the weight like I mentioned was a MAJOR factor. But as much as I wanted to shave weight I ultimately "have" to have "great" photos, and to that extent the Fuji DOESN'T disappoint one bit.
I hope this if nothing else makes your final decision with one of the options you presented above more "cross-referenced" for lack of a better word
-I swore the next lens/camera purchase I was going to make was the 35 sigma, not one bit disappointed not having it even though I desperately miss my 35L....
-fuji x100s as a secondary to the 5d3 is a great idea IMHO and based on my experiences with my Fuji you will love it.
-I have NO experiences with Leica, other then laser distance finders so no comment or comparison here
- regardless of what you buy and ultimately travel with I am certain you will have great photos and have a total blast!!