1. Any player who is going to explore what it means to follow a code of conduct in a game (or for clerics a deity, religion, philosophy, or similar) should write that themselves. Think of it like when magic users make their own spells or fighters their own maneuvers. At start cleric players choose what their deity is and why they believe in it. They can have a schism later, if they don't like Mr. Potato Head anymore, but this can be done in game. Initially the design should largely be left up to players. This doesn't mean a loss of powers however. It means a changing of deities followed and probably a change in powers available - certainly the spells available suite. It isn't like Paladin where the class is actually lost, though it might be for a shorter time until another deity is chosen and the cleric is re-ordained. Seeing how Paladins are one and one I would think clerics have it much, much easier.
2. I'm against small penny pinching of a point system where all the wavering up and down the alignment track constantly shifts the power of a character class. The executive powers granted worldly authority in modern times isn't that fickle; deities typically take a longer view than us. The game is designed in levels rather than point-based powers for just that reason. It also simplifies the DM's tracking. If groupings like class or levels are lost, then losses come in bunches. That's much easier to handle. All that said, if you want to do it, then you can for your game.
3. Fitting deities, moralities, and cultures into boxes of 5 or 10 things isn't the way to go. Build for flexibility. If I only have one overriding edict I must follow, but that edict is extraordinarily stringent, than the gains in response to following it are that much more regardless if it is only one.