If you wish to reduce income disparity, you will necessarily have to reduce production disparity - for the former is generally the consequence of the latter in a market economy. Competition for productive resources will drive the price paid for those resources ever higher (encouraging production and ensuring that such production falls upon the most efficient utilizer of such production).
Interesting point. The problem is that even leveraging automation, it is impossible for the blue-collar worker to out-produce the CEO because the CEO is deemed to be responsible for all of the production of the workers under him or her. Sometimes CEO bonuses don't even seem to rely or performance measurements.
If income disparity really was tied to productivity, I would not have a problem with it. Workers would naturally gravitate to jobs where they are more productive and thus paid more.