This actually sounds like it could make for a great system, in the sense that you still maintain the original quality and quantity of output, but you still get to avoid the burnout of that 20% completely, because after some time, it will be somebody else's "turn" to do more heavy-lifting. Obvious problems here are that 1) company/team structures in industry don't seem conducive to this, 2) skill levels are unequal, so to maintain the quality of the 20%, one would need to plan carefully to account for this -- but, it also seems like a good way to help lower skilled workers rise to meet higher standards -- and 3) hinted at before, this needs to be institutionalized in a tangible way, and that seems to require a difficult form of team member assessment/introspection that managers may not be capable of facilitating.
Wrt point 2 above, I've heard from sources I trust (but would have to bug them for specific sources on this) the following phenomenon has been observed in education: when you remove top performing students from sections of a course -- say, to join an honors section of that course -- the non-honors version of that course has a void for high-performance students. Interestingly, this void is often filled by the mid-tier students who would have typically performed at B/C level, and now some of them will rise to perform at an A level. It would be fascinating to find observations of this in the industrial setting as well. If I find a source for this, I'll update my comment.