Politics are interesting. Perhaps politicking wouldn't be necessary if we could determine with accuracy the results of policies before implementing them. For example, maybe this could be done by complex computer simulation in the future. Furthermore, policy might be synthesized by the same processes if it can be simulated. Which then raises another interesting point: would democracy be less efficient and necessary if…
Of course, plenty of partisans have an interest in producing models that spit out results that just so happen to show what they already believed (e.g., Tobacco Institute), and politicians will cite those results with the same regularity as more rigorous work. Without expertise in the matter, it can be hard to find any given model's weak points; and they all have weak points.
As for voting for desired outcomes rather than desired policies: I'm pretty sure this is what most people are doing already. Lots of political pressure all around have your cake and eat it too. Sadly, I've never seen any policy that could solve a problem like that--too many trade-offs in real life.