Classic changed Enchanting Recipes

Arbitration made me aware of an issue we will face in the 50-60 bracket.

Most of the classic enchantments for caster classes got changed with wotlk, while they required items like "nexus crystals" before (disenchanted from classic items) they now require "prismatic shards" (disenchanted from TBC items only).

This is true for most other ingredients as well (Elemental items, Dust etc).
Is it possible to change the requirements in a recipe? Not without Core edits right?
What are our possibilities here?
### 1) Try to change back the recipes to classic

From my understanding since these spells are saved in the client there is no simple way to just overwrite these with sql values in the DB. If I am wrong please correct me here but I think this would require a custom patch.
### 2) Make an exchange vendor

We would need to find out if there is an almost 1:1 way to exchange the materials to the classic values. Like @Yehonal said this might be possible to do without core edits but I am not sure.
### 3) Make an exchange gossip NPC

If the option of using a normal vendor doesn't work we could script a simple exchange gossip NPC. Same principle as for option 2, we would need to research first if the items can be exchanged 1:1
### So what should we do??

We need to find someone who has the time to compare the classic recipes with the changed ones to find out how we could exchange the items accordingly because from my understanding changing the recipes would mean too much work and a custom patch. So option 2 looks like the preferred method.