re: Lunar ice difficult to mine?
WEll, having lots of heaters will certain increase the energy requirements and make the process that much more expensive.
Also keep in mind that many experts think the "ice" is in pretty low concentrations within the regolith, maybe only a percent or two. I've heard it compared to the water content of dry concrete; "ice caps" is probably NOT the way to think of it. You probably are talking about a major industrial operation, not just shovelling ice into a bucket the way you more or less could on Mars.