If you are ever going to grant Bretonnia Rites just like the TWW: 2 factions have, might I recommend the following ideas?
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CALL THE PEASANTRY:
Duration 10 turns, cooldown 5 turns (so 2/3th of the time it can be up). Cost: 2500 gold
You gain +10 max Peasant Economy And +2 local recruitment, in addition, your Peasant mob units are boosted in the following way:
All Peasant Mob units have their Upkeep cost reduced by 50%, have their Casualty Replenishment increased by 25%, have their recruitment duration reduced by 1 (minimum of 1), and have their Leadership increased by 15. In addition, all Peasant Mobs their attacks will deal Fire Damage and cause the "Blinded" effect. To simulate their pitch Forks and Torches, as they attack their opponents eyes and blind them with fire.
This will turn it into a fun little themed Rite, which would make Peasant Mobs be worth picking in the mid to late gam, as easily replaced chaff that can still be useful. They will pretty much be the ultimate meatshields: Very low stats, but with a debuff that allows them to last longer and let your other units be more impactful.
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CALL OF ERRANTRY:
Cooldown 25 turns. Cost: 6500
This will be based on the Errantry Wars from the lore:
https://warhammerfantasy.fandom.com/wiki/Errantry_WarYou will summon an Errantry army at your capital that will function like a Death Night Voyage, and be unbreakable and require no upkeep, but you can't exchange units nor directly control it (only assign their targets), and they can't replenish their units. You may only have one of such Errantry army at a time. This army will always consist out of 8 Knight Errants, but they would be led by a Enchantress with a trait that boosts their performance, and each state of Chivalry adds another trait to her that improves these Knight Errants. The rest of their army could consist out of non-Cavalry units, and which kinds of units are in it depends on your level of Chivalry. Any settlement they take will fall directly into your control. The Prophetess her level would increase based on the amount of Chivalry that you have as well. Once you have reached maximum Chivalry, you are allowed to manually control your Errantry army, and they may finally replenish their units.
(This way you can have a army of "Starting knights that mean to prove themselves", and still let them be useful in the mid to late game. Because their army composition, level of the Prophetess, and the additional traits that she has that boosts her Knight Errants is increased based on your Chivalry. So while 8 of the untis will always be Knight Errants (the rest varies), the Prophetess will gain additional traits that makes her Knights Errants even stronger based on your Chivalry. This will be a form of Death Night that scales based on accomplishments instead of giving you an all powerful army from the start, but which allows you to choose targets).
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BRETONNIANS UNITE!
Duration 10 turns, cooldown 10 turns. Cost: 3000
For the duration you gain +4 untainted, +4 Public Order, +25% increased Campaign Movement range, and significantly increased chance to confederate with other Bretonnian factions.
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Perhaps the Fey Enchantress could then also gain a Faction trait that decreases the cost of all of the Rites by 50%? (similar to Lord Mazdamundi).