I disagree only because the way the power structure of the bow is laid out, so I would say you where correct If was just handing a bow with a laundry list of abilities. but the way I am laying it out is that the item would only work if the player chose to use good actions, otherwise it would be a normal longbow this would end up being a magor con littming the power of the bow. furthermore, the item would have a level structure its self in which the power and abilities would progress much in the same way a class skill try would, and would mirror in some way that of the power class try for a paladin of that level; furthermore, if it only has say one ability add or two at first level. how then would that be overpowered as the level structure for the bow would be another limiting factor to the power of the bow. a third limiting factor would be how powerful the abilities that I choose to give the bow, so if the lower bow level abilities are weaker gain strength as the bow scales then that would limit its power as well. also for the charcht its self narratively speaking when this item is found and for the player it would fit well with their own back story.
The other assumption is that I would railroading the player into LG, and the direction they would want to go. This would not be in fact the purpose of the angel spirit, but it would rather be that of jimmy cricket in which the bow acts a kind of wise sage guiding the character while still letting the character and player have free will to make their own choices. the bow its self has its own free will not only with choosing weather or not it would want to be used by the player or allow the player to use its abilities, but it could very well chose to leave the player seeking out another member of the party or an npc to go. the other factor is being a LG alignment item it would not seek to control the charter only an evil align item would make such a move, and also a sert it will on to the character case in point the evil blad grog wild that tried to eat his soul. also being the agnel would be a representation of Sarenrae and follower of the paladin code or taints of the ever light church it would go against what she is about. I feel given this and the character has free will to keep or lose the bow it would fallow up to the player weather or not they would keep the bow itself.
As I said scaling is everything about this item, and i'm not just going to hand a player a nuclear device at level one to see what happens. but I will keep your points in mind, thanks for the heads up.