I'm starting with the cleric class, this is just a taste.
Cleric
Ceremonies: Ceremonies are special holy rites that a cleric has mastered that resanate with divine power, but are not spells. At first level a cleric picks one, the cleric picks another at third level and at every three levels from thier.
Example Ceremonies: Turn Undead, Exoricism, Consorecrate/Desorecrate, Fattawa, Blood Sacrifice, Divine Marriage, Channel Divinity, Convert, Commune, Ridden, Prophecy, Sin-Eating, Lesser Investure, Greater Investure, Vow of Poverty, Vow of Chasity, Vow of Sin.
Gnosis: As your faith grows so to do you grow closer to your God or Philosphy, the connection becomes stronger. Still Gods are too large to grasp in thier entirety and so ypi seek union by becoming one with aspects of your God, aspects called domains, which are facets of you god or philosphy. A Philosphy or God's Domains may or may not manifest as unique beings, such as saints, avatars, manifestations, or angels, etc...
A Cleric gets access to one of thier Gods Domains at 1st level, 5th level, and every 5 levels after that. Each Domain gives profancies and a domain gift that requires 5 minutes of mediation to reattune to after being used before it can be used again.
Orisons: Orisons are O level cleric spells that can be cast at will. A cleric chooses one at 1 level and gets one with each domain. The Lesser Investure Ceremony allows a cleric to grant the use of one of thier Orisons to another person who they invest a measure of thier power as a Champion of the Faith. Only one person can be so invested for each time the cleric chooses Lesser investure as a ceremony.
Spells: As normal cleric spells. Retains words of power, but slight change in fluff, Words of Power are the secret sacred names of your God/Philosphy, invested with power and unspeakable to unbelievers. The spell works the same no matter the God as all Gods have these Secret names/words of power becomes thier appart of a God's Godhood the way a true name are apart of a mortals soul.
Rituals spells change a bit, reduce the cost of ritual spells by 25 percent for each partipate other then the caster. Particapates need not be spells casters to be invovled. Rituals that use a holy relic are free and recieve bonuses.
(Authors note part of the goal here of the Cleric was to make the cleric feel more spiritual, give it a more religious feel, instead of A armoured wizard who prays, so I tie the features more into side effects of spiritial growth, instead of just using Domains as just ways to make a cleric more unique, I'm using them as stepping stones on the path to divine union, Ceremonies harken back to the fact that priests can have different duties within the same religion)