I’d like the ability to:
A) Combine multiple columns between various boards with customization of values
B) Get rid of duplicate values (especially true for columns like Country)
C) Allow for multi-board charts to make associations with each other to decrease duplicates
What are you trying to achieve
I want to make charting better and more elastic. See my next comment for a picture of option C.
Maybe try the Smart Spreadsheet app — it does exactly what you need!
When you add it as a widget to your Dashboard Hub, you can import all the boards connected to that hub (depending on your monday.com plan) and reference the columns you need in a separate spreadsheet to build the chart you want.