I've planned out a rough development road map for the Minecraft plugin, researched the libraries I'll use, and out down the base code as well. The current version can be loaded by the latest version Spigot server and will start and connect to the standalone server.
I'll post a proper update or a link to more updates in the OP soon.
Always interested in hearing about it, as Minecraft is probably one of the only games which gives enough freedom to implement something like this. In fact, I believe many have attempted, and partially succeeded in the past. You are probably aware of it, but I believe there was a server which integrated Bitcoin, and had Bitcoin payouts for things like mining in Minecraft. There was also a casino inside Minecraft, which I believe might have closed down due to legal issues, I'm not entirely sure on that though.