The BMPCC isn't well-suited for long-form video. To get the best out of it, you're shooting DNG at about 4 gig a minute. It will give the best low-light performance, in my opinion, because the image is uncompressed, so shadow noise become film-like grain. However, the problem with RAW video is that IF you're getting the benefits out of it you're getting an image you can't get with other compression-in-camera cameras--so matching becomes a problem. It becomes your A-cam and your b-cams look too contrasty.
The crop factor of the BMPCC is 3x, vs 2x of the MFT. So a NIkon 24mm becomes 72mm on the BMPCC and 48mm on the GH4. It's a drag!
BMPCC internal audio is not really usable, so plan on syncing everything in post. When the Sony a7s comes out, that should be an exciting camera for that kind of work. The ability to re-frame a 1080 image, from the 4k image, in the gH4 would probably be VERY helpful in weddings and concerts.