Thanks for the quick replies.
He is very interested in getting Charisma to saves

, and not much else it seems.
I've considered opening up the Paladin class to other alignments, and/or simply refluffing it.
It seems to be the best way of solving the problem. However I'm unsure on how to implement it, should I just let him chance his alignment - and let him keep his abilities. Maybe change some of it around as Hex0 suggested.
How to best implement this change within the game? Would it be best to simply ignore that he has fallen in the past, and just say " well, now you can be a paladin of any alignment - so you can't really fall".
Or should I implement and legitimize this change using the story, eg. you find a new god/teacher who opens your mind with new possibilities.
The party is pretty standard CN/TN - I feel a blackguard would be pretty out of place.
Well the thing is, the player really wants to play a Lawful Good character - it's just that the paladin's code can be a little restrictive and sometimes very harsh.