Sorry, but apart from food rotting over time I think all of these ideas are bad. For example the taxes, instead of making the money magicly appearing in the nation owner's bank they should hire people to collect taxes. Also having limits to mine sizes is a bad idea as well, there would be nothing stopping people from mining wherever they want to. On the subject of removing money from mobs maybe limit it just to skeletons and zombies who were once people so they might had had money on their person when they died. Also don't have currencies for certain races, if you want different currencies have them for different nations. Like the currencies if you want to have resources for each race make the resources for each nation, otherwise people could just have a nation with all different races so they would have all resources