The goal posts should definitely be fixed! And maybe some politicians would want to pass a law that benefits him and his friends in some way, even though it only has a small effect, so there ought to be some kind of safeguard against that, too. But the main problem I can see is anti-synergy. Suppose a law is adopted that totally would have worked, were it not for some other law that was introduced a little later? Should the first one be repealed, or the second one? But maybe the second one does accomplish its goal, and repealing the first one would have negative effects, now that the second one is in place... And with so many laws interacting, how can you even tell which ones have which effects, unless the effects are very large indeed? (Of course, this is a problem in the current system too. I'm glad I'm not a politician; I'd be paralyzed with fear of unintended consequences.)