There are schemes like this in Brainstorm which get voted highly because the voting and discussion doesn't include those who actually know the details (and complexity) of the possible implementations.

Similarly, discussions about karma are limited because of the technical limitations with the current karma system. Unless, in discussion with the folks who can implement it, the scope is increased into a full-blown redesign of karma (the biggest technical limitation at the moment, AIUI, is that the entirety of a user's karma is recalculated from scratch every time. It does not accrue).