Choosing between OM-D E-M5, GH2, and NEX 7/6 for documentary/photojournalism photo AND video

I have posted about this in the Micro Four Thirds forum, but I also want to include the Digital Video forum since I am also considering the Sony NEX 7/6...so if you have seen this post before, skip to the second half for an update based on previous suggestions...

(The long story...) I am embarking on a year-long trip to the Amazon rain forest area in Ecuador in a few weeks and need advice. I am pursuing photography and video that falls somewhere within documentary and photojournalism (interest being social issues and human rights advocacy). With this intent, I am expecting my needs are having light gear that is also somewhat rugged (due to the wet and humid rain forest environment), carrying as little gear as possible, and using gear that allows me to be as discreet as possible. Video is also very important to me, so I’m attempting to being able to capture the best quality video with room to grow without sacrificing the other factors. Finally, my funds are what I have been able to save and I have no clients or income from what work I will produce at this point (hoping that will change). So to be clear, I am a beginner starting with zero but aiming to eventually do professional work.

I am only interested in mirrorless systems and am considering either the Sony NEX system or the Micro Four Thirds system, though I am leaning towards the Micro Four Thirds system for its lens selection and weather sealed options. Thus, I am considering either the Olympus OM-D E-M5 for weather sealing, still IQ, and IBIS, or the Panasonic GH2 for video IQ and affordability, or the Sony NEX for size, still IQ, and video IQ.