This is already the case for Master's degrees and above in Denmark. I've been the opponent examining students. We ask Master's students to give US instruction on a topic (drawn randomly on a card in front of them, from a list they know a few days in advance). They do a chalk and talk on a topic for about fifteen minutes with three to five professors being "dumb students". It works fantastically and at the end it's very apparent to both student and teachers how well a topic is understood. Marks are rarely contested and in my experience most students think the process is fair.
Of course, woe betide those with social phobias....
Of course, woe betide those with social phobias....