I see the integration between Rally + Miro as truly a step change in helping with defining work items in agile teams backlogs (Backlog Management v2.0).
Business Agility or Enterprise Agility there is a lot of work done at the portfolio/program level backlogs. The current Rally + Miro Integration is just at the User Story/Defect level.
If the integration could take advantage of creating/synchronizing a Miro Canvas with a Rally Portfolio Item (think Strategic Theme > Initiative > Capability > Feature) that would be tremendous for Divergent <> Convergent Thinking/Problem Solving/Strategic Thinking/Solution Design methods used to help define/refine items in the Portfolio/Program backlogs.
Maybe the canvas represents the parent Portfolio Item/s (example Initiative/Epic), and cards could have the option to become a child Portfolio Item (i.e. Feature etc.) too.