Custom maps WITHIN the official game map

So with the custom maps being made, what if they could be linked to the official map through some door or corridor? This way we can expand the official game and make it feel like we have more areas to explore. There are many doors that cant be opened in case that cant be entered. What if the custom maps can be entered through these formerly disabled entrances?

I think the best thing that can be done for rage is to make the actual game world more expansive and explorable with more liberal areas and details. For example, so I can make a custom room for a house and then somehow link that with a previously unopened door in the official game.