Gathering Idea + Gem store.
Why is this better than taking those X amount of gems, turning them into coin, and buying the materials you want on the trading post?
In practical terms, this sounds, as Felbryn observes, an awful lot like a more complicated version of buying gathered materials off the TP. The extra flavor/work might be fun for some, but, since buying off the TP helps grease the wheels of the economy (creating demand for materials, removing via TP tax, etc.) I don’t think the potential fun is worth the trouble.
It’s certainly an interesting idea, and might even be fun, but all the micromanagement is also work, and it’s very difficult to judge what the value of such a thing would be, over just spending the gold on materials from other players.
How is this different from a bot programmed to harvest from a map?