I spent a lot of time testing different configurations to make the FP more ergonomic. I finally found the best cage and drive to keep it, relatively, compact without going down the Dark Labs rabbit hole...
With that said, out of the box, the camera isn't much bigger than the original eos-m, so when you add a cage, the ssd, lens adapter and lens, it morphs into a much larger camera that isn't much smaller than my 5D3 but much more cumbersome.
The screen is pretty nice on the FP and excuse the pun, but with the 5D3, you can see the "magic" of raw on the LCD. With the FP, although it's a better screen, the image has a very flat, dimensional look.
Battery life isn't that great with the FP either, compared to the 5D3... I'd say you can get about 45 minutes, or so.
In some ways, the FP would probably work better if fully rigged out or if the barebones camera was on a gimbal with the SSD attached to the gimbal's handle.
With my current setup, I'd say @BTM_Pix 's approach using M mount lenses would probably be the most compact route. I've been looking at some LTM lenses, so we'll see.
In a perfect world, I'd have the money to buy an R5C or R5ii when it gets released, but that doesn't seem likely, so I'll decide what to do with my FP.
To tell the truth, if someone offered me a good price, I'd consider selling it right now. I got OpenAI for video now.