"imperial fealty" could be just "fealty" because I suppose you won't draft only Sardaukars?
I should clarify; the official party line was that Sardaukar were recruited from levies. This is what most people believed. The reason why I mentioned this is because it demonstrates that the Great Houses did in fact have to give feudal levies to the Emperor.
However, in reality, Sardaukar did NOT come from these levies, they were recruited solely from Salusa Secundus, the emperer's hell-hole prison planet.
give the Imperium belief the ability to use a landing stage to get a sardaukar contract and let the "temples" increase espionage
I don't really like these. Imperium "temples" should give happiness and culture, and slots for nobles (which are boosted by the Imperium shrine).
Sardakar cooperation should remain a Corrino-only thing. But the Corrinos should have a high rating for the tech that founds Imperium and prefer to follow that religion, so they will naturally be more likely to trade their Sardaukar resource to other co-religionists.
* * *
So, a variation on the original design:
1. Galactic Empire
Idea: The ethos of preserving the feudal galactic status quo, and supporting the Emperor as head. This is an early game religion that is founded by an early tech and is easy to spread, but can be easily overtaken later by any of the other ideas for change.
Gives culture and happiness; people like the status quo.
Can be founded by or adopted by: anyone but Fremen or Tleilaxu
Founded by tech: feudalism
Great shrine: Imperial palace. Adds +2 free noble specialist, +1culture per city with this religion, +1 gold to all noble specialists. Spreads religion. Can be built by great priest, great noble.
Unique buildings: Feudal estate. Gives +1 happy, +2 culture, +20% culture. Allows 1 citizen to be converted to noble. Requires tech: feudalism.
Fiefdom. Gives +50% culture, +1 happy, +1 happy if Landsraad is state religion, +1 happy with Sardaukar cooperation resource, requires 3 feudal estates. Allows 2 citizens to be converted to noble. Requires tech: imperium.
Unique units: Diplomat. Standard missionary unit. Requires feudal estate.
Special properties: High spread rate, high spread rate from shrine. This religion is automatically removed from a city whenever any new religion is planted in that city.
2. Landsraad
Idea: ethos of trade, particularly spice, controlled by the Great Houses of the Landsraad. Spice makes CHOAM go around.
Can be founded by or adopted by: anyone but Fremen or Tleilaxu or Bene Gesserit
Founded by tech: great houses
Great shrine: CHOAM Headquarters. not actually a shrine, but instead another spice corporation hq (and no executives to spread it), that competes with all the other spice corporations (so you can't have both in the same city). Spreads CHOAM religion (not the same as the corporation). Founded by a great trader or a great priest. Gives +2 trader GPPs.
So this allows you to get a second city that gives +3 commerce per spice resource you control.
Unique units: Emissary. Standard missionary unit (spreads the religion, not the corporation). Requires CHOAM outpost.
Unique buildings: CHOAM outpost. Gives +1 trade route, +25% trade route yield. Allows 1 citizen to be converted to trader. Requires tech: spice economy.
CHOAM Directorate (cathedral replacement). Requires 3 CHOAM outposts. Gives +1 trade route, +50% trade route yield, gives +1 happy from each of the various luxury rade goods (semuta, opafire, etc.) Requires tech: CHOAM.
Allows 2 citizens to be converted to trader.
Special properties: This religion requires creating both a religion (the main component) and a new corporation (which shows up ONLY as the replacement for a holy shrine). Low natural spread rate, low spread rate by shrine, normal price missionaries.
3. Messianism. (Alternatives: Way of the Mahdi, Way of Muad'Dib)
Idea: Jihadist. Convert the galaxy by the sword.
Founded by: Holy Jihad tech.
Can be founded by or adopted by: anyone but Corrino or Tleilaxu
Great shrine: Dune Messiah (or: Prophecies of the Mahdi). Gives -100% war weariness in this city. Gives -25% war weariness empirewide. Gives +10% military production per city with this religion. So the shrine becomes a unit factory powerhouse. Gives +1 priest GPPs.
Unique units: Fish speaker. Requires theocracy. Strength 6 melee unit, very cheap on hammers, death does not cause war weariness. Designed to be cannon fodder; lower strength than contemporary units, but able to be fielded in overwhelming numbers.
Unique buildings: Temple of Muad'Dib. +1 happy, +1 culture, +15% military production, +1 unhappy per non-state religion. Allows 1 citizen to be converted to priest. +10% military production with Fremen water debt.
Special properties: no missionary unit. Low natural spread rate. High spread rate from shrine. Whenever a civ that has this as its state religion conquers a city, this religion is automatically added to that city.
4. Tleilaxu Supremacy
Idea: Tleilaxu should be apart and separate, with their own theistic faith that they will never share with outsiders. Essentially, this is a religion that can only ever be adopted by 1 civ. Its main purpose is to encourage the 'Otherness' of the Tleilaxu, and the fact that everyone hates and fears them (diplomacy penalty for different religion with every other player).
Can be founded or adopted by: Tleilaxu only. This is the only religion the BTl can adopt.
Founded by tech: mysticism (so you get it in your capital).
Great shrine: Prophecies of Bandalong. +4 culture, +2 free priest, +1 hammer output to priests and great priests in all cities. Allows 2 citizens to be converted to priests.
Unique units:
Unique buildings: Zensufi temple. Adds +1 happy, allows 2 citizens to be converted to priest. Requires Faith.
Biology lab. Adds +15% beakers, +1 happy, allows 1 citizen to be converted to priest. Requires Academies tech.
Axolotl tanks. Requires genetic manipulation. Allows 1 citizens to be converted to priest.
Special properties: no missionaries. No automatic spread or spread from shrine The religion is automatically spread to any new city founded by the BTl faction. (Several religions in Warhammer mod work like this, so I know its codeable).
5. Qizarate
Idea: Bureaucratic religion leading towards the golden path.
Can be adopted by/founded by: anyone except BTl.
Founded by tech: some mid-late-game tech. Academies? Or a newly created Qizarate tech?
Great shrine: ??
Unique units:
Unique buildings: Quizarate temple. +1 happy, -30% city maintenance. Allows 2 citizens to be coverted to priests.
The Golden Path. Gives +5 happy, +5 health, -25% beakers, -50% trade route yield. Requires golden path tech.
Special properties: When spread to a city, it instantly eliminates all other religions in that city. Does not have a natural spread rate, is not spread by shrine; missionary only.
6. Way of Shai-Hulad.
Idea: the kind of general animist worm-worship held by the Fremen before Paul, and many of the regular inhabitants of Dune. Basically a weak backup religion for anyone who doesn't have another one, or for players who would rather get a standard gold-shrine religion.
Can be founded/adopted by: anyone except BTl.
Founded by: Faith
Holy shrine: Shrine of the worm. +2 culture. +1 gold per city with this religion present. +2 priest GPPs.
Unique units: Prophet (missionary replacement).
Unique buildings: Arrakian Temple, +1 culture, +1 water, +1happy with Fremen water debt. Natives of Arrakis with traditional lifestyle use less water and so have some excess. Allows 1 citizen to be converted to priest. Requires tech: faith.
Special properties: missionaries more expensive 50% more?, low religion spread rate. This is an inferior religion. Shai-Hulad doesn't answer prayers.
7. Technocracy
Idea: a techno-industrial complex leading back towards thinking machines. Technology bonuses and production bonuses, but happiness penalties (the people don't trust the machines)
Can be founded/adopted by: Anyone except Bene Gesserit, Bene Tleilaxu.
Founded by: Industrialism
Holy shrine: The Great Processor. +2 culture, no GPPs (its not encouraging human development), +25% beakers, +1 beaker per city with this religion. Can be founded by great prophet, great scientist.
Unique units: Technocrat (expensive missionary).
Unique buildings: Automated factory. +25% hammer production, +1 unhappy. Allows 1 citizens to be converted to engineer. +25% hammers with power. Requires industrialism tech.
Computerized research center. +25% beaker production, +1 unhappy. +25% beakers with power. requires cybernetics tech.
Robotic power plant. Provides power with Thinking machines resource. requires thinking machines tech.
Special properties: Low spread rate, no spread rate from shrine. Expensive missionaries.
* * *
So, some synergies can be obtained by giving bonuses with the unique trade resources.
We could also take the Technocracy buildings and rather than having Ix get UBs from them without the unhappy, just give +1 happy with thinking machines resource.
Also thought of a cool Bene Gesserit idea:
Unique building (Bene Gesserit): Missionaria Protectiva. +1 culture. Gives +2 culture +1 happy per religion present in the city.