Depending how big your 'hub' room/area/level is, you can do it without any scripting at all.
For example, if it is a single room, you can create a prefab of that room (instructions for creating prefabs are in the FPSC manual) and, using that same prefab in all your levels, arrange your levels to begin and end at that prefab.
Your prefab can have several doors leading in to and out of it, and each level will begin and end at a different door in that prefab.
I've used this method with great success in my own game, Seclusion.
If you have any questions about this method of using hubs, feel free to ask them