There is no reason to go with the headaches of using the Black Magic Cameras. The quality out of the GH4 and probably today out of the NX1 is more than enough to film anything, including fiction. Any difference can only be perceived in side by side comparisons by people who are doing just that, side by side comparisons. Frankly, a tiny bit more dynamic range would not make this more interesting, just the life of the shooter and the editor more complicated. If your subject is interesting, if your story is captivating, nobody is going to have time to wonder if the trees, that we can see outside the windows, from inside, are fuzzy or perfectly in focus and clear. Who cares?
Once you can buy what the GH4 and the NX1 can give you, don’t entangle you in the world of Black Magic to gain something nobody will see. Focus on content, lighting and get it right while filming, that way you’ll minimize working with colors in post. And no, the H265 is not a problem, just convert it to prores.