Just so we are all clear: I would recommend that you use this mod with a copied savegame file if you are very concerned about a rock appearing where it shouldn't.

Here is my answer to those frosted up windows inside (almost) every interior cell in the game.

Name: Reneer's Interiors Mod

Version: 0.99

Requirements: Latest Oblivion Patch, All Natural / Natural Interiors, OBSE 19+, and "Base" file.

Description:
This mod intends to allow the player to view outside scenery from inside interior cells. This includes landscape, buildings, lights, sky and water - though water will need OBSE 19C+. This mod will also allow for landscape viewing outside of the cities – so long as the windows of the interior cell are transparent.

This mod is still beta stage – it requires the use of PlaceAtMe, but also uses OBSE's DeleteReference command to minimize as much as possible any bloat that may occur using PlaceAtMe. While I have not noticed any save-game bloating, I advise that you test this mod on a new / copied save.

Screenshots:
See TES Nexus page for screenshots. I'm rather fond of http://static-1.nexusmods.com/15/mods/101/images/35897-2-1291598168.jpg that I took early in the mod's development.

If you have any screenshots you would like to submit to the mod's gallery, please feel free.

Changelog:

0.99 – Overhauled the object detection system, which should remove most of the problems of other buildings finding their way into the interior space.
0.95 – Tree problems should be fixed. Fixed an issue with interiors being improperly rotated 180 degrees opposite to the outside exterior.
0.94 – 'Floating object' issues should be virtually eliminated now (though some exterior objects may not be moved into interiors). Landscape issues are still being examined. The mod now ignores Ayleid ruins and basemants without using name-based searching.
0.93 – Most issues regarding meshes being improperly placed inside interior spaces should be fixed – one issue that still remains is landscape sometimes poking into interior meshes.
0.92 - Major bugfixes, many interiors should function properly with little mesh collision occurring.
0.91 - ESP file update.
0.9 - Initial Release.

Download:
http://www.nexusmods.com/oblivion/mods/35897/? (version 0.99)

Note: The "base" file is very large (~250MB). Updates to this mod will likely only include minor texture tweaks and ESP files, so you (should) only have to download the "base" file once.

Could you explain what you mean about a rock? Does "a rock appearing where it shouldn't" mean that we are likely to see rocks appearing in interiors? Is a rock static some kind of workaround you use to make this mod function (like coins or calipers in inventory)? I'm not sure I understand what you are trying to say here.

Rocks aside, this sounds like an interesting mod. I will certainly check it out the next time I play Oblivion.

What I mean by that is that sometimes the object detection system might not find a particular object (a rock, for example) and it will appear in the interior "space" (the building). This should not happen nearly as often as it used to in older versions, but it is still a possibility. Any objects improperly added to the interior "space" will be deleted from your save-game along with all the other "added" objects. Much larger objects, like walls and other buildings, should never appear in the interior space.

This is one of my favourite Oblivion mods

Yay!

Thanks for putting this out.

I seem to recall that there was an issue with some places (i.e. churches) being flooded in the previous version due to being below the water level of their interior cell. Was that issue fixed in the latest release?

Yes, that was also fixed.