My world is built on competing priesthoods, I'm not 100% that's a good idea.

[Eldan]

How about instead of thinking primarily about different gods when creating nations, you think about different kinds of nations first, then think about how the different priests might work in them?

Don't just make monarchies, is what I mean. Have a Republican city state with Senate, where noble families hand out political offices like general and governor and tax collector to their favourites. Have a theocracy, where king is also high priest. Have an elective monarchy, where after the death of the king, there is a one-year interregnum during which the nobles haggle for power and gather supporters. Have a nomadic nation with tribal leaders, who only occasionally unite under a khan for a migration or a large raid. Have a highly decentralized empire, where all the real power lies with Dukes and Counts.

All of those give you a lot of leverage points for your priesthoods.

Then, an entirely different point, how about sacred locations? Sites of pilgrimage for the different gods, that also mean there is a steady source of income and influence for one god over another? This is the clay pit where Korus breathed life into the first oxen to plow the fields for an especially loyal worshipper. This is the very rock in which Khemra's holy fire carved the first letters to teach mortals how to write. It still glows brightly after all these years. This is the spring of Mera's tears, that cure leprosy. This is the mountaintop oracle of Nami, where anyone can listen to the winds, which will tell them where to travel to find new purpose in life. This crater is where the first mortal defied Greymoria's love, gaze upon it and tremble. And so on.