Braking with the left foot - absolute disaster, for the reasons already mentioned.
I suppose it would be possible for a young person, taking appropriate driving lessons, to learn the technique, but then, how would that young person then drive a manual car?
I'm afraid for us 'oldies' having driven normally for up to 60+ years, it is impossible.
And so, to repeat the first question, WHY? I can see no advantage whatsoever, and many dangers!!