At moment alignment is only meaningful for what weapons the character can use. I think that's a little boring. So here my idea: Give players a bonus if they play their alignment (like in dialogue choices, I have discussions like the one with Dead Girl at Delara's Graveyard in mind). What bonus? Maybe more XP in certain quests, more special items, extra favour or some quest (chests, doors or what have you) that can only be opened if you have a certain alignment. And of course there should be a way to change the alignment in game (with certain quests or the hard way by taking choices that are showing another alignment, second should be only occur if taken too many choices that are not in line with your alignment).