In Tropico 5, there was several quest chains in sandbox mode, where player needed to complete several quests to certain person/faction. These quest chains always had wacky story on them, few examples:

His Royal Majesty tries to build worlds largest bonfire
Export fish and cans to Cthulhu worshippers
Try to get Pope visit Tropico and later try to get him leave

My idea how it would work in Tropico 6:

First era has one quest chain and later eras have 2-3 that player can/must complete. First 3 eras would have 10 different quest chains, modern era has 15 and they are randomized each time.

For Colonial Era, quest chains are similar like they were in Tropico 5: Produce/export certain goods to the Crown so their Royal Majesty can do something stupid. Crown has 10 different quest chains.

For World Wars era, if player wants to ally either Allies or Axis, Tropico must aid them in major battle or in special mission, like exporting food and guns to French Resistance. Both side have different 4 quest chains and there's 2 additional quest chains that doesn't involve alliance.

For Cold War era, if player wants to ally either Western Powers or Eastern Block, Tropico must help them in secret spying operation or in special mission, like exporting Soviet nukes into Tropico. Both side have different 4 quest chains and there's 2 additional quest chains that doesn't involve alliance.

For Modern Era, if player wants to ally any of the foreign Powers, Tropico must do something special for them, like trying help them recover from economic crash (of 2008) or help them in War of Terror. Each side has different 2 quest chains and there's 5 additional quest chains that doesn't involve alliance.