- Include religion percentage by cities. This is more realistic and can add new concepts to the game like minorities. It can be linked with an ethnic percetage by cities.
- Include tribal religions (100% in a city before founding a religion) and atheism.
- The settlers should spread religions to the new founded cities.
- Give a higher bonus from an homogenous religion within a city and official state religion.
- Include religious events based on religion diversity: unhappiness, terrorism, spread foreign cultures.
- To prevent consequences from bad religion events add new concepts like sacrifice, evangelism, inquisition or cruzades. These new concepts should encourage state and local religion.
- Sacrifice would be the posibility to take war prisioners and kill them for religious spread (war prisioners is a new proposed concept in military improvements).
- Cruzades and inquisition should be implemented in Civ 5, they will spread and preserve religion, maybe they could be implemented as civics.
- Preserve the missionary unit.
All these posible implementations should come with changes in religion bonus, diplomacy and economy.