I've been poking around in Minecraft lately (1.7.10, where all my favorite mods are still at), and I'm finding myself growing a bit bored. The thought occurred to me, I'd love to see some kind of mod or combination of mods that makes the surface inhospitable. For example, a burning sun that makes you take damage in the daytime, or frequent meteor showers, etc.
I've seen a number of mods that make the underground more challenging (Glenn's Gasses is a new favorite, along with Hardcore Darkness), but I'd love to see something that challenges the player to build their home mostly underground, making short surface expeditions into a necessary evil.
Any suggestions on mods to help someone achieve this kind of environment?