Well, this one is pretty simple to say but probably not so simple to implement because, when you enter a house a.k.a new cell, being able to see exterior happenings in real time would be memory hog. All the scripts from the NPC's would have to keep running, along with the other processes that govern the outside world I guess...
Nevertheless, I hope that Beth will maybe implement it, if they can...So, here is my vote for it...
Cheers!
You kind of shot yourself in the foot. Setting the game up this way would simply take too much time, as you would have to gut out over half the internal cells (the ones that are for houses, shops, ins, guild halls and other buildings, construct internal components for each building (forcing you to be a bit more cookie-cutter as you would have to work with a set of generic buildings OR you would have to make a TON of different buildings), and THEN re-design the internal design of the buildings, including ALL components of the quests that have ANYTHING to do with something inside one of the affected buildings.
This isn't something that I wouldn't even mod into the game as it would take a LOT of effort. But the memory-hog thing? As long you don't have garbage dumping problems with the engine(ahem, New Vegas), then you're fine. Scripts will only run when triggered or with OnGameMode, which means that the script runs when you're in the cell that the object is located in. Stuff like background operations like AI processing, physics, quest scripts and object rendering are the major resource users.
It IS something that you can pull off, but you would need about six months to a year to make an Alpha for it, then more time to make a Beta and a bit more time for a final update, and that's with a team of artists, programmers and designers (if you want it to kick ass and keep Mr. Hat from smacking you up). That is too much time and effort for most modders (if you try to rebuttal this statement with a mod that does this for Oblivion, note that I said MOST modders, not ALL modders) to even bother with it and will make it impossible for Beth to implement it correctly and stay within the timeframe they gave themselves. If they did this, it would either be crap or they would go FAR over their Veterans Day mark.