I fear that adding all of these attempts at further reflecting sounds off of the ceiling is going to degrade the overall sound stage into an undesirable mish-mash.
What will a driver firing upwards from the top of a tower do to music listening? Perhaps it might work; however, I think that this would upset the balance & imaging that the Axiom folks work so hard to achieve...
TAM
There is a thread over at AVS by Scott Wilkinson about his experiences with Dolby Atmos during demo's by Dolby and at theaters. A top firing speaker would be wired separately from the main drivers and be driven by its own amp channel and would not play unless fed information from the Atmos decoder.