2. Random encounters which incorporate AREA, like the cafe of broken dreams. You can't just poof these into game because the player may have already been to the area where you plan to poof it to. You can provide a door to a new cell though, because that cell can be off map. The encounter could start by you seeing someone in a party hat slip through a door that wasn't there before. Still there is a new door, but a door is a lot easier to overlook than a building, etc. Tis represents static changes to the map, and it's difficult to accept that they weren't there before.
I wonder if there's really any need for a random location event to pop up, though. For example, Cafe of Broken Dream, or what have you - it could just be placed beforehand in the game world without needing a random event to spawn it. It could just be something you come across in walking the Wastes. Like the Alien Craft we have in Fallout 3 - it's pretty random that you'd be walking through that specific area anyways (and the mechanic of the radio transmissions they did nicely in this game - so you know you're getting close to an area like that.)
You could add a mechanic where it places random area encounters into the game, or you could just as easily have those already existing in the game and just be something you'd stumble across on your way to places. The effect would be the same, anyway. If I'm walking from Megaton to Tenpenny Towers and I come across the TARDIS, does it really make that much of a difference if it was something I'd have seen just because I was walking past the place where it is, or if it had decided to spawn there? (Actually, TARDIS might be a bad example, as that's small enough that it could qualify as a spawning encounter the same as people.) But if you wanted a random encounter of a haunted house- you could just as easily have a haunted house in the game that you could stumble across.
But hey, either way it would work is fine with me. One question, though: I'm having trouble visually what you mean by a "door." Like instead of passing by one of the boarded-up houses, you notice it has a door that signifies you can now go into it? Or a literal door standing by itself in the middle of the Wastes (hey, if it's one of those side-joke type encounters I don't think that would be much of a problem.) Or do you mean it figuratively where that door could be anything that signifies you moving into an instanced area?