This is very interesting - thanks for posting!

I think you may have hit upon something here that is little well known. I personally have not encountered this multi layering of dreams - but, it makes sense to me for a number of reasons:

- when you meditate in the day or just phase out/daydream you may come across random 'waking' hypnagogia, which I think shows that our 'subconscious' is dreaming all of the time, even in the day and we just need to 'tune in' in order to access it
- many believe that there exists several planes of existence, all multi layered and on top of one another (the astral, mental,buddhic etc) this may be crossing ideas but also may be corroborating what you are suggesting.
- this would help to make sense of information transferred and received within shared dreaming