What I posted in the main thread, plus what I added since in red

It seems that there are a lot of or could be a lot of different items for each spirt beast, especially with the above list in effect, there could be anywhere from three to five decently powerful items (not considering certain parts come in multiples, such as claws or teeth). Perhaps say that after dying, a beast will dissolve in to the spirit world, and that it requires a spell of x-level to preserve a piece of the beast to make into something, so that you can't get a bunch of different items from each beast, and this can only be performed once in the time it takes the beast to disappear.

Or maybe these items wouldn't be powerful enough for this to be in effect.