Oh I love that idea, thats actually better than the "Trade-Up-Contracts" take I had because like you said, with the recipe approach you could constantly and more importantly -> easily add new sets to the expansion.

However finding those recipes must also be balanced so that players who own only one or a few plots dont get frustrated because its too hard to find those 🤔

Maybe there could be "common" recipes that create items&spells randomly from a large list and by doing quests or work the lands you can find "legendary" recipes that are only usable one-time and they are more expensive resource-wise but give way better outcomes.

And you could also add some sort of potions you can use to increase chances of certain abilities or splinters or rarity (also a good opportunity to dilute the rewards players get to counter bot farms)

Like I said, I really like that idea of yours 😊 Many ways that could work, cause for me the goal is to make land as immersive as possible so it offers a variety of angles you can play 👍 So thanks for sharing that :)