The LACE Suggests using Labels to represent each Portfolio Epic, and the use of the component field for the value stream. Any value can be added to the labels or components field, but labels are their own dimension in the EZBI data cube, allowing reporting across teams and projects both within throughout the enterprise. A label name would be created for each new Portfolio Epic, and the teams and programs delivering the program epics would assign the component or label for work items down to the feature level (maybe lower?)
The label or component field could be used to provide additional levels of granularity as needed, possibly to provide insight into operational areas of concern where multiple teams support a single system, ie., Cloud Services,
At the portfolio plan level, a team could be created to represent each LOB or other division so the program epics and features could be represented in the plan.