This is possible without having to use lots of map files, I am currently doing it in my mod. My maps are made up of lots of 21tilex16tile rooms and when you walk to the edge of the room the camera slides to the next room. I do this by having a blank NPC in the centre of the room and having a <FON command set to it, meaning the camera will only focus on that area. When they walk to the edge of a room it triggers a H/V Trigger which sets it to focus on the next camera, this causes the nice sliding effect.
It can also work if you want your rooms to all be different sizes because you can set the camera to <FON a H/V Trigger and then just control where the H/Z Trigger goes using those No NPC blocks. That way you could have a long corridor that slides as you move but doesn't leave the set boundaries.
Finally, if you want your rooms to have actual doors to go through you still can do this without lots of map files by just having the door move you to a different spot on the map instead of to a whole new file.
Hope this helped in any way. If you need to get more detail I could send you some map files with the script so you can see how it actually works.