More advanced technology -> more efficient administration -> more stability limit on overextention. That makes sense for me. If you wanna go for historicity, it's more logical to remove historical tiles from oversea empires. Or make year of Africa event which cause colonies to become independent. Or, considering how the mod just fails to properly simulate modern history on fundamental level, just foget about historicity and enjoy the game instead of proposing something which will make life harder for the player and do only that. Cause AI doesn't care and anyways will massively die after 2020, cause that's how this game works.