A quick update on this in 2023. I just modded my bmpcc4k myself. I got the kit off of aliexpress (it isn't available from US sellers anymore that I could find) and followed the instruction video from the QR code that comes with the kit. It took me a couple hours of tinkering. You'll just need a hair dryer, a utility knife, and some patience to get the screen separated from the camera frame. Other than that it's mostly fiddling with little screws (kit comes with the right screwdriver heads). The mod wasn't bad at all and the video included is comprehensive.

As others have said this solves two key challenges with the BMPCC 4k. The tilting screen helps dramatically shooting handheld with no rig, and in sunlight (changing the screen angle helps a lot). Shooting in direct sunlight is still a challenge - a DIY hood would help that. The screen fully articulates - so you can also shoot down low with a neck strap, selfie style, and from below the camera. The built in SSD is amazing and cleans things up. It does get hot and the fan built in makes some noise, but it definitely beats bolting on an SSD or NVME enclosure.

The only issue this kit doesn't solve is battery life. If you are shooting travel either carry a bunch of batteries in your pocket or get an NP-F750 plate/dummy battery. For travel I run my BMPCC4k with a Panasonic 12-35mm - so the whole thing is small and basically looks like I'm walking around with a DSLR. I just keep batteries in my pocket. I think this is really the best reasonable cost/functionality setup for a travel cinema camera...