This is interesting data points that should be taken, and added to the big discussion thread (that apparently fell off the bottom of the world a while ago) where the best guess server side stuff was discussed.

1. You'd have to have all variants of a model unlock from redeeming ANY one of the set, not require any one specific item.
2. You can't just have it unlock when somebody briefly holds an item. This isn't wow, we don't have "BoP". So we'd need to redeem the item from circulation, otherwise one crafted dyable item could be passed around the entire world and only one would need to be crafted ever. So, we'd have to have a catalog redemption item. Then it would have to be used on the item to scribe it into the catalog.