You will miss the C100, trust me.
The BMPCC4K/6K are goods cameras on paper but they are a totally different story in real life situations.
First, to have a "usable" system you need:
Cage + extra grip: Mandatory. Add a handle at least.
External monitor: Mandatory. Add batteries for that.
Cast or external drives: If you're going serious and also you're planning to use a gimbal, you should go for at least a couple of Cfast.
Battery/Power solution: Of your choice between at least 8 to 10 batteries or 2 to 3 VMount for a full day. If you use a VMount you need extra rig and plates to mount them on camera. But if you use a Ronin-S you can't use VMount batteries (ok, you "can" but why would you do that to yourself...) Maybe a mix of VMount with some LPE6 will work. Energy will be a pain with this camera.
Lens Adapters: Add a Metabones if you go for the 4K and a good set of NDs or a variable ND for your lenses.
Follow Focus: If you will use a gimbal you will need a follow focus like the Tilta.
Now you have a ideal set for shooting, just like me a few months ago until I decided to sell everything because of how ridiculous everything went from an initial $1200 USD "inexpensive" camera. Money is not the bigger problem of this camera, it's the clunky rigging, the stupid battery system (worst problem of the camera imo) and the overall feeling of "this camera will collapse in any minute from now" when you finished the rig and start shooting (because it's true, a fully rigged BMPCC4K breaths unreliability).
I think that you will be better with a Canon C200 (with RAW, "good" codecs and AF) it maybe wait for the new cinema RF line.