Sounds good, until you get to the point of trying to define each of those concepts in a way that is not tied to this universe.
What does "medium" mean? What is a "base material?" Where did it come from?
Beyond that, you still haven't told us how they got there in the first place.
You're just speculating: making some assumptions about how you think it might be.
So before you go feeling all proud of yourself for stumping those silly folks who would posit a "Creator," you might give some attention to the fact that you're in the same boat.
No I'm stating the theory
Besides, I don't "believe" in multiverses. It is just one possible explanation. If I were to "believe" that they existed I would need evidence.
All it is is positing a *source* without it being an entity to which one may have to answer.
You're just speculating: making some assumptions about how you think it might be.
Which is NOT science.