So here is an idea on a new spell and components for it. This spell would be on every spell casters spell list.
Craft Magic Item
3rd-level transmutation (ritual)
Casting Time: 8 hours
Range: Touch
Components: V, S, M (3 components of rarity equal to the rarity of magic item) consumed
Duration: Permanent
You turn a non-magical base item into a magic item. The exact formula needs to be worked out between the caster and the DM. Every magic item needs three components of a rarity equal to the rank of the desired end rarity of the magic item.
For example to enchant a normal sword into an enchanted sword of uncommon rarity you need three components of uncommon rarity and a sword to be enchanted. The components are consumed in the casting of the spell.
Making a magic item is exhausting work, you take a level of exhaustion for each rank of magic item you are forging. So making a common magic items causes 1 level of exhaustion, making a very rare magic item causes 4 levels of exhaustion.
You can not make artifacts with this spell.
Casting at higher level.
The 3rd level version of this spell can make only common magic items.
4th level uncommon, 5th rare, 6th very rare, 7th Legendary.
So now the DM just populates his world with magic item components of different qualities and gives those out as treasure. To combat the take every bit of every monster ever thing, just require that most of those types of things need to be "fresh".
Already existing magic items can be substituted for missing magical components of the same rarity.
An example.
Paraxis a powerful wizard wants to make an uncommon quality item, a wand of magic missiles.
He talks things over with his DM, spends some time working out the right formula or researching an existing one and discovers he needs 4 things: the essence of will-o-wisp, a jewel possesed by a banshee, a dart used to kill a man, and a good quality base wand.
Now during game play the DM could have just handed out X number of uncommon components as treasure, like some DM's hand out X number of 200 gp gems, or the DM could have Paraxis and his companions have to quest for each of those distinct items. Paraxis could also choose to replace any of the three components with another uncommon magic item.
After the components have been gathered Paraxis casts the spell, it takes 8 hours, all the components are consumed in the casting, because it is a uncommon item Paraxis has to use a 4th level spell slot and when it is done has two levels of exhaustion.
This system lets beer and pretzel style, bash in the door type play exist next to long term campaign style. The DM controls how often components appear, what those components are and if he wants to track very specific things or just hand out generic components as treasure.
I would also make a lower level of the spell and have different components for potions and scrolls. I will work on Brew Potion and Scribe Scroll spells later.