I personally think if alignment is to be added it should be something picked at character creation and is not referenced that much. Maybe it can open up dialogue choices like other tags or be affected by or detected by items and spells but otherwise doesn't have a large gameplay impact.
You can play a chaotic evil person doing good actions if you rationalize them. Maybe they take the quest to save those innocent people from goblins because now he has a social excuse to slaughter something and inflict pain and while laws were not constraining them the threat of being hunted was. And you can roleplay a lawful good character doing something evil, perhaps he buys a slave off of a slaver because he rationalizes that freeing them this way is better than freeing them by force but all he is doing is rewarding the bad deed of the slaver even if it is legal in that city.
Therefor I think it'd be difficult for the game to track morality per actions without just boiling them down to good and evil when a large part of dnd morality is Intent. By such a system it would flag a devil doing something generous as good even though the intent is to eventually trap someone into a deal for example.
