Crafted-only Magic Items for Pathfinder

    I was talking to a fellow GM a few days ago and he told me a story about a time when he had tried to help out a player by creating a specific magic item, only to have that player turn around and sell it.  I've run into that before, magic items that either I made or choose that ended up going to waste - and it happened a lot when rolling on the random treasure tables.  Which got me thinking, what if there was an easy system to let players pick their own magic items, so that they would always be something useful, but still limiting that player's power level?  I think I have something, it sounds easy on paper at least :)
    First, some back-story: magic is the primal living force of the universe.  While inanimate objects can hold magical power, they cannot use it.  So every magic items needs to be bonded to a single person.  It them becomes an extension of that person and cannot be used by anyone else.  The owner of a magic item can choose to sever the bond, which leaves the item ready to be bonded to another.  But, if the owner dies, the magic of the item follows them into the outer planes and the item becomes non-magical.  To prevent losing this power crafters, and then adventurers, carry octagonal crystals that capture magical energy when it's released.  This energy can be used to craft new items, and is a form of magical currency.
    Okay, so the rules.  Whenever an NPC is killed and they have a magic item, the party does not gain the item as usual - instead the party collects Mana Resonance that has the same type as the arcane school of the magic item, is rated at the same GP value (measured in "beats" since the crystals that collect it seem to pulse like heartbeats when filled) as the item's value, and has a GM-applied type.  For example, a magic flaming sword would have the evocation (I think, going off what I remember and not the book right now) school, and the GM would add the "Fire" descriptor to the Resonance collected.
    During downtime between adventures the party can use Resonance to create new magic items.  The Resonance has it's full value applied towards the item's value if it is the same type as the new item, or half value if the new item is a different type from the resonance.  So the Fire Resonance above would be worth full value towards making a new fire sword, or a ring of fire resistance, but only have half-value towards making a shocking sword or ring of acid resistance.  The rest of the cost can be made up from other Resonances, or gold.  Exactly what items can be crafted is up to the GM, so not every community may be able to craft every type of magic item (since the skills of craftsmen and scholars will logically vary by community).

    And that's it.  Mechanically this should work the same.  After all, you'd have the full value of the flaming sword if you took it and used it, or half it's value if you sold it.  So this should keep the same ratio of power.  You could add a small fee, like 5-10% of the new item's value in gold (and/ or Resonance) since it is a bonus to be able to make/ choose your own magic items.  Crafting could be the same, you just need half the item's value in the right Resonances - but honestly I think this kind of needs a crafting revamp, I just can't think of how exactly at the moment.
    I can see a fun way to use this system, if a magic item is destroyed when the owner is killed, then it might be fun to have the party require a magic item that is already bound.  That way they can't just kill the owner, and they can't steal it (no "command words" that anybody could use, items only obey their owners in this system) - so they have to figure out how to convince/ trade/ blackmail/ something the owner to help them.  Also, there could be items just lying around, that were never bonded or that previous owners had relinquished, and if the PCs want one, they have to get to it before anybody else or it could be lost to them forever.  A bit of extra tension to liven up the story.
    So there you go.  This mostly uses the existing rules - you can ignore the extra type part if you want to make it easier with no extra rules/ bits to track.  It should keep the same general power levels, and restricting what kinds of items can be made where can keep the party from being able to make anything game-destroying.  Heck, you could give crafters a bonus and say they can spend Resonance during an adventure to make a one-shot magic item like a potion or scroll, if you wanted to give your crafters some love (which also conflicts Resonance as a resource to spend now for an emergency boost or stockpile for later to make a permanent item).  Also magical creatures could drop Resonance, which might make a little more sense than finding random items on them.  So I think there is lots of potential to help make a more magic-friendly system (which may not be your style of game, of course) with minimal rules overhead and a low risk of unbalancing the game.  At least, in my head it seems that way - if you try it let me know.