This is a very good take as to how the Phases of the KINGDOM HEARTS franchise could differ in deeper explorations of elements.With how many elements of Versus XIII Nomura is choosing to rework for Kingdom Hearts, dreams are definitely a likely one. Dreams were supposed to be an element of FFXV, most likely a holdover from Nomura's version, but were cut sometime late in development.
With phase 1 exploring the heart in dozens of ways, phase 2 exploring dreams would be interesting, and he could definitely connect that with DDD.