Simple enough idea: Each door in Skyrim takes you to a randomly selected place. The front gate of Whiterun might take you to the Riften Sewers. Or the Valthume Catacombs. Or the area to the left of the Thalmor Embassy. You don't know until you walk through it. This would make selling items and crafting much more difficult, quests a matter of luck, and render much of the game unplayable. Or rather, make it into a different game. As for implementation. I'm sure getting the game to truly choose locations at random would be either impossible or too nauseating for anyone to bother with, so a preset list of possible locations, one of which will be chosen each time, seems much more practical. The over-world, rather than just being a gigantic room where the player can avoid doors, could instead have a timer on it, that upon counting down, teleports the player as though they had walked through a door. As far as I can tell, this would be a relatively easy mod to code, with most of the difficulty coming from the task of making the list of possible places, and perhaps the RNG required to make the choice.
