I feel that the father you get away from the fantasy view of black and white you will find out that there is more shades of grey to consider. I have done away with alignment in all of the campaigns I have run since d20 modern has came out and have used the allegiance system. Alignment is still in the the allegiance system but it doesn't dominate if it was just itself. This would free up those classes that require a alignment to have different options to be defined by, such as a Paladin that has an allegiance, basically a marine that has been in the military for his whole career, to his country instead of a set lawful good. His powers, spells and abilities would come from his belief in his country and all that it does for others countries as well as it's people. As for the Monk it would allow them to properly do the many different philosophies of martial arts that was taught throughout the world. As for the Druid they would have an allegiance to nature instead of neutral. Allegiance isn't perfect but it is better than Alignment for anything that isn't fantasy or black and white.