I would love to see a more 'survivalist' type of RPG with known dangers when you're out in the wilds.
Among my favorite mods for Oblivion were some that allowed you to fletch your own arrows and create leather armor from the skins taken from wildlife. Heck, I think I even made a small ranger camp, just for the sake of immersion at playing someone who is a survivalist
So having things like snow storms, avalanches, slippery slopes, falling icicles (in ice caves), hypothermia and more such things; they would be able to add a ton to the Skyrim experience! Make 'setting up camp' a requirement when out in the wild, chop/find wood and make a campfire to keep warm when in the colder regions of Skyrim etc.
Greetz,
Milt