It's kind of annoying that there're 3x3 dark tunnels scattered around my base due to random players mining, and I would feel bad accidentally doing the same to another player despite it being a great way to level up mcmmo mining. Similarly, random chunks of sand/dirt peeled from the surface (probably mcmmo excavation) looks really bad!
So I think a mining dimension that reset alongside the nether and end would be a great addition to the survival server.