That CCTV video also reminded me of this discussion which, as I recalled correctly, went nowhere.
I have zero experience with any of those projects and thus cannot really contribute much to a discussion. But I do think it is very interesting. And hope they progress to the point where the price can perhaps come down and be within reach.
A modular digital camera just makes so much sense — from a user perspective (but probably a lot less so from manufacturers’?). I would generally ditch 90+% of the features of a camera if I could just get a bigger, brighter viewfinder and the ability to swap in a native B&W sensor when I want it.