I seem to recall you can enter this mode with the console, but the engine crashes if you are not in an exterior zone. Combat is next to impossible (but you can enter VATS and possibly survive) due to the controls still being geared to your FPS or over the shoulder view. As I mentioned above, there was an RTS mod that used this mode exclusively for building bases and it tweaked the controls a bit.
Here's the mod: http://www.nexusmods.com/fallout3/mods/7070/?
The images give you some idea of the view (it's not that bad). The mod basically makes FO3 a different game and I'm thinking some of the FO4 settlement features come from this mod.