In the style of
https://www.warlight.net/Map/15406-Issanders-New-Europe-2-Population-Density-bonusesand
https://www.warlight.net/Map/17599-Asia-Population-Density-bonusespossibly balanced for GDP/ PPP per capita to mitigate huge populations?
using EU4 style uninhabited voids
inserts/ blown up areas for greater densities (eastern seaboard, asia)
I have little map making experience, but would be happy to help build one