Space Pope
The mega-church mechanics civics work really well to act simulate being a head of faith kinda like the pope. The main focus is spreading spiritualism for the glory of faith (and simony) by any means necessary. Focus on spending the Energy to promote the faith either by supporting fellow spiritualist empires or through the Galactic Community gives a usage to accumulating resources that is less selfish.
A fun and unconventional twist is to worship a Fallen Empire. For me, it basically started as a joke in an MP game played back in 1.6 but I uttered the words "Have you heard about our Lord and Savior Mr.Fallen Empire?" so many times that I'll never forget them. Now that the Sion Origin exists, this is an actual possibility since there will be a guaranteed Spiritualist FE, and bringing another empire into the fold is kinda similar to force converting them to the true faith.
Criminal Reclaimers
Using the Remnant origin as its background, your empire was born after the collapse of an empire. From the ashes, a criminal Syndicate emerged, restoring order and taking over the state duties. Now that things are somewhat stable on the fallen capital, it's time to reach back to the start and reclaim the old empire's glory.
The reclaiming part can be done in multiple ways.
- Using the Chosen One event to transition you out of the criminal heritage.
- Forming an Hegemony and calling it X's Empire.
- Become the Galactic Emperor.
Of course, there is also the possibility of mixing those for a gradual transition.
This of course requires the Criminal Syndicat origin and preferably an authoritarian leaning to form an Hegemony. Focusing on a more vassal/federation playstyle to build up the empire rather than direct conquest work best considering Megacorp's penalties when going over the admin cap and makes for a change of pace.
From a gameplay perspective, Criminal Syndicat is really good at rushing Ecumenopolis since they can spam Branchs way quicker than other megacorps assuming the galaxy is not a hug-box of xenophiles. Those branches will eventually get closed, but having an early Ecumenopolis provides such an advantage that it's worth the hassle. Becoming the galactic emperor as a criminal syndicate also work very well in the late game.