Why would that be a bad thing? Sounds like you've just described role playing. Not playing as yourself but as a someone who adheres to a particular moral code.
I would consider role playing more that you develop a character and then do what they would do in a situation. Having an alignment gauge would cause player bias. If the character does an action that they would consider good but the game considers it neutral or evil, that seems to bother a lot of people and they would replay that part doing what the game considers good even if it is not what their character would do.
I have never tried to play a character with such a rigid moral code that they only follow that, and don't care if the best and possibly necessary thing to do in a given situation is what "should" be done. I would expect that if I did try this that any DM would throw situations at me until my character grew up and realized things did not fit into neat little boxes.
You know what would be an interesting aspect of a game? If someone designed a game that could take such rationales into account.
This would be interesting but sadly probably too much work to cover all the possibilities.
