I'd love to see the mod take a somewhat different approach to religion in the future.

The big change I'd like to see is the addition of specific religions and the de-emphasis of religion type. There are a lot of ways these could be implemented, but I see some of the following as viable options:

a. At least one religion is added to any empire with a specific state religion type selected during empire creation. Some empires could have more than one religion. Typically, a religion should have tenets that follow the ethics of the originating empire when the game starts. All spiritual empires should have at least one dominant religion and possibly other minor religions. Non-spiritual empires could have minor religions.

b. Allow religions to be created mid-game. Mid-game religions would be created based on the tenets of a faction within an empire.

c. Pops should adopt religions the same way they adopt ethics, but independently. A pop with a religion would be drawn to the ethics of that religion (in this way, a minority faction could become powerful if they create a religion that spreads among the people, drawing them towards that ethic). Likewise, pops will be drawn to religions that support their ethics.

d. Religions can spread between empires, so evangelizing a religion that follows ethics you support would be a way to subvert another empire's civics. Supporting a faction would also emphasize any religions that are based on that factions ethics while de-emphasizing religions that aren't, since there would be more pops of the supported faction in the empire.

e. Adjust the way flexible and dogmatic paths work. Instead, a dogmatic empire would have one state religion it could pick (from among religions present in the empire's population), while a flexible empire wouldn't focus on any one religion. Mainly, the state can support one specific religion and be able to build up that religion's effects via the religion council interface, or an empire could be welcoming of all religions, which would reduce the effects of those religions on the empire's ethics attractions, allowing the empire to have many religions in harmony.

f. Each specific religion should offer some minor benefits to the pops that follow it. These can be things like output increases or decreases, happiness, and resource upkeep changes. Whether the government of the empire supports or oppresses that religion would impact how strong some of those effects are, and a highly supportive empire might cause pops to gain additional positive effects. Pops with religions that aren't the state religion would contribute to instability based on their political power.

Overall this would make religion a new mechanism to manage stability and ethics attraction, while also introducing a new dimension for interstellar politics. Further additions beyond these basics could include conflict between religions within your empire, wars based on religious differences between empires, a more elaborate process for the creation of a new religion starting with a sect or schism, offering support to religious groups within other empires, changes to migration and refugee mechanics based on religion, federations based on religion, and so much more. Getting the foundation right would be the first step though!