Part of Dorico’s way of thinking about music includes the notion of “blocks”, which I guess are somewhat similar to parts in Cubase, i.e. blocks of content that can be moved, duplicated, and reused. Our end-game for blocks is to allow things like repeated passages of music or ostinato passages to be linked together, so that changes in one place affect all of the other linked places, but there is a good deal of complexity in this area – conceptually simple things like having a tie extend out of the end of a block actually cause a great deal of complication (particularly because, in our music model, a chain of notes tied together is actually stored as a single event, as if it were a MIDI note).
So blocks will be lying dormant under the surface of the first version of Dorico, waiting for us to unlock the functionality that they will provide in the longer term.
As for higher-level arrange-type operations, I would certainly not rule them out. To begin with our conception of the arrange-like display in Play mode is really to allow tweaking of playback of music that you have created in Write mode, but it could absolutely develop in that direction in future versions.