I would cross out the Scarlet-W right away. You are looking at $15K minimum to get up and running and the waiting time is very long. I know because I ordered many months ago and I'm still near the back of the queue with no allocation in sight. Moreover, the RED cameras are not ideal for documentary, have very poor on-board sound options, and would introduce a steep learning curve for someone who shoots primarily with a Sony A7RII.
I would also stay away from the C500 + RAW recorder option unless you have used this exact combination before and know all the quirks involved. There are simply too many things that can go wrong here. In addition, adding the recorder means that you lose the hand-held advantages of the Canon bodies, so it really defeats their purpose for me.
If you can afford the C300 II, and you don't need 4K HFR, I would definitely choose that option. Otherwise, the FS7 is also an excellent choice and has much better slow motion than the C300 II. You can't go wrong with either one of those. Best of luck!
It sounds like the Sony FS7 gets asked for a lot and has industry recognition. Personally, I think the C500 producer much nicer images, the C300ii as well.
K Jonathan Park reacted to Kino in Canon C500 Is it worth 7K new?