The communism tech decreases happines from the improvement in the cathedral slot. Maybe you can use it.
Also having temples and cathedrals without giving the civ the ceremonial burial and monotheism tech makes them inactive.
You can't make buildings(improvements) obsolete-just wonders.
Invention changes the people to renaissance.
If a civ has no access to the future tech the game crashes.
The navigation and magnetism techs decrease the chance to get lost at sea.