Why not E mount
Then you could use speedboster and adapt any other lens. With EF there is no such option...
I don't really get this move by panasonic
It is for photos and 1080p video (and still in 1080p it's not good in low light) but not for 4k. So yeah in RL FullFrame sensor does not guarantee good low light perfomance.
Since OP said "...Full Frame sensor can handle much higher ISOs than a Micro 4/3 sensor without increased noise. (Ex: Micro 4/3 at ISO 800 = Full Frame at ISO 3200)..."
And 5Dmk4 has similar ISO perfomance as Micro 4/3 camera (like new panasonic cameras)
"...Of course all of this depends on the kind of sensor your camera has; a Full Frame sensor can handle much higher ISOs than a Micro 4/3 sensor without increased noise. (Ex: Micro 4/3 at ISO 800 = Full Frame at ISO 3200)... "
You must know a bit more than that.
That is why FullFrame Canon 5Dmk4 is worse than a6300/X-T2... for low light.
Crop factor and codec are important and probably some other things.
5Dmk4=Bad codec+1.7 crop factor+? = bad lowlight
So fullframe sensor does not help here much.
A7RII is better in crop mode than in fullframe mode
A7S is better in fullframe mode
So yeah it's a bit more than a sensor. You really have to test it.
There is less moire but other than that I would say that video is the same.
So yeah this is 2016 and I would not buy 1080p(does it even have 1080p detail ?) DSLR to shoot video.
Just go with panasonic or sony
Like your whole movie has to be shot in only one room