Reporting: Aggregating Amounts by Region in a Flat Entity Hierarchy

Hello everyone,

I’m working with a flat entity hierarchy and need some help.
I have entities like FRA1, FRA2, GBR1, and GBR2. In a cube view, dashboard and/or spreadsheet, I would like to aggregate the amounts by region, such as FRA (summing FRA1 & FRA2) and GBR (summing GBR1 & GBR2). However, I would like to achieve this without creating a new hierarchy.

Below is a representation of my goal:

Do you know of any ways to proceed with this?

Thanks in advance for any help or suggestion!