So to be clear, you don't want Paladins to be required to be LG? So if the DM says "your Paladin is no longer LG", it just means writing something else on your sheet, not losing Paladin abilities, or any inability to continue leveling as a Paladin?
As long as your "trait" based is strictly a roleplaying aid, it sounds fine to me.
The Paladins are a special case - the alignment restriction has been on them forever (even though I can see them working fine without it).
But yes, I want the "trait" to be purely a roleplaying aid.