on the bp point, i don't know. all existing systems at LHR and MAN require a bp to capture and check, so on capture it links your photo with your bp and at any subsequent check point it checks your face against the one held against your bp. i guess in theory you could have a system which didn't link to a bp, so you capture on coming off the flight and when you get to the UK/CTA channel to bypass immigration you just check whether the person matches any of the photos in the system. not sure how quick and accurate it would be tho if it is comparing against hundreds of photos vs one.

I suspect it is the former tho, which as you note means folks would have to retain a bp which they won't be used to doing and creates the problems you note.