I like the idea of leveling weapons or magical items, but if a fighter can use a weapon for a long time, pay xps to improve the masterwork weapon to a magical weapon, nobody really needs the feat craft weapons and arms.
If a fighter can create own his permanent magical weapon it reduces the need of spells like GMW, Magic Weapon etc.
1.) I would limit the bonus of creation of a magical weapon by a crememony by a fighter to a maximum of a bonus of a GMW spell of a caster of the same level of the fighter -1
A fighter level 9 can only create his own +2 weapon.
2.) A fighter can only create a magical weapon with a bonus and not special properties like flaming burst, returning, etc. For creating a magical weapons with special properties the fighter needs the feat craft weapons and arms and he must use the wepon on several times in a situation apporbiate to the special property (e.g. returning ability for an battleaxe, the fighter must have killed several enemies by throwing his axe.)
If a fighter can create own his permanent magical weapon it reduces the need of spells like GMW, Magic Weapon etc.
1.) I would limit the bonus of creation of a magical weapon by a crememony by a fighter to a maximum of a bonus of a GMW spell of a caster of the same level of the fighter -1
A fighter level 9 can only create his own +2 weapon.
2.) A fighter can only create a magical weapon with a bonus and not special properties like flaming burst, returning, etc. For creating a magical weapons with special properties the fighter needs the feat craft weapons and arms and he must use the wepon on several times in a situation apporbiate to the special property (e.g. returning ability for an battleaxe, the fighter must have killed several enemies by throwing his axe.)