I had an idea for an MMO where you'd have spells take the form of a sort of computational currency like BitCoin. What I mean by that is, you'd build some multi-staged, difficult puzzle as the spell creation system (not necessarily an abstract puzzle - it should be things like the mana wires, genes, etc systems). When you're done building, you can compress the spell into a 'packet' which then just has some resultant mechanics in-game that are basically invisible. The trick is, you can teach someone your spell, but they just get the packet, not the design or the ability to teach others.
So this creates an in-game marketplace of the best spells to do X or Y or Z, where players can create resources for the marketplace by coming up with better/more efficient solutions to the spell mini-game. This provides some disincentive to posting good spell diagrams on wikis and the like, which means that figuring out the subsystem can remain as a longer term part of the game-play experience.
Whether or not it would be fun depends a lot on the implementation of the puzzle and of what the spells actually do in the world though. And while there's kind of an academic interest in the economics that would result, I'm not sure they'd actually be enjoyable to experience as a player.