Dear Roger,
Very interesting ideas you bring up and certainly worth studying. I had looked at the sphere possibility but discarded it in the past. I may reconsider this given the way you put the idea.
But... there are still some conceptual problems. You talk of "exert pressure", "prevented from...", etc. According to Newton's third law, only something that has mass can exert pressure or prevent another thing from changing its shape.
Then overnight I considered your grouping of spherical building blocks, in day to day thinking there will be space between them. If those spaces are non-existent how can their spherical shape be attributed to them? The spherical shape is CONTINGENT on the EXISTENCE of something between them.
Your analogy of books is very good and easy to understand with familiar things. Even then SPACE an existent separates the covers of the two books. If nothing existent lies between the covers, the two covers will be one cover.So books can be separated, but when it now comes to space, THE SEPARATOR itself, what will SEPARATE it, when it has a discrete representation? Who can we look up to to do the separation for us? What does not exist cannot separate it. Although for the universe as a whole I agree with you that the non-existent can be its boundary. These difficulties have tantalized philosophers for a long time, (i.e. One or Many). You can enjoy a writing on Parmenides/Zeno [link:classics.mit.edu/Plato/parmenides.1b.txt]
Best regards,
Akinbo