Maybe neither the character's intentions or actions should have much to do with the alignment as written down on the sheet. Imagine, if you will, the great Powers of Law and Chaos, Good and Evil. They sit across from each other at the great gaming-table of the gods. They move their pawns about the surface of the worlds, and sometimes between the worlds. Each one has a great many pawns indeed.
Now. Focus on an individual Pawn. Let's say a pawn of the power of chaos and good. That individual pawn need be described in no way as either chaotic or good. He could be an oppressive commissar who cares for nothing but the letter of his iron-fisted code of law. But, in his ultimate destiny, he will end up serving the cause of chaos and good. Perhaps because his excessive actions drive the people to revolt, perhaps because he is so blinded by his creed that he ignores the insurgents in his own household. In any case, he is a pawn of the powers of good and chaos, and he serves their whims regardless of what he might think or intend. But when he levels up, becoming another of fate's darlings in the form of increased ability to cheat death and force his desires upon the world, it's Chaos and Good that have made that investment in him.
The player would write 'chaotic good' on his sheet, and if anyone hit him with a Lawful weapon he'd get the shock of his life when its magic harmed him.
I experimented with this idea a couple times.