The Inception one wouldn't be too hard I don't think. Barring any real issues, it could be made to work pretty easily. I can think of a few different ways to do it as well, though the method I would use would involve NVSE, as that would be the easiest by far.
Warning, minor tech talk following.
Create a list of all beds in each wasteland. Continually search (each cell change) for more beds to add to the appropriate lists to allow for mod beds. Track the bed that was slept on so we can return the player there when they sleep again. The starting wasteland is the 'real' world, and sleeping there will take you to a random bed in the dream world.
Same as above with lists, but build them instead as the player plays the game. Starting world is again the 'real' world, and as the player explores their alternate dream world, process all beds they come across for any return trips.
The simplest method. Track which bed the player sleeps in in either wasteland, and return them there each time. Maybe not as random, but would allow you to more easily resume where you left off in the 'dream' world.
I'm a big fan of randomness, but I think it'd be much more enjoyable from a gameplay perspective to use option 3. Which again is the simplest method to implement. The only downside I see from this is that if you want to enable the full start from either game, it will take some editing of the tutorial quests and startup areas to keep from conflicting with the char gen. This particular method also lends itself best to a NV first style of game, where the CW is a flashback dreamland that the player visits.
A pretty cool thing to implement would be a autosaves on sleep, so that a death in the dream world results in reloading at the sleep. If some method could be used to detect this type of event (it IS possible), then it could be used to restore the player's sleep on reload, and prevent them from sleeping for several hours, to force continued gameplay in the 'normal' world. Kind of like having a nightmare and not wanting to go back to sleep.