Although there are likely more than enough roles in the kingdom for anyone who is playing Kingmaker, I believe in the saying that "the more roles the merrier."
Things to keep in mind when brainstorming:
-What positions may have been necessary in a medieval kingdom? In a fantasy kingdom?
-Game Balance (If these positions are added to your game, you may want to increase the difficulty class for some rolls)
With each newly presented role, I add a Note disclaimer to warn players what roles the new position may be stepping on.
With that disclaimer; here are some of my ideas:
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Counselor/Magistrate
Note: This may step on the territory of the Ruler, Grand Diplomat
Provides legal advice and presides over legal issues.
Benefit -Increase economy by 1/2 Counselor's CHA or INT
-Increase loyalty by 1/2 counselor's CHA or WIS.
Vacancy Penalty- Decrease stability by 3 (Or alternatively increase unrest by 2... Unrest seems very important however so you may want to go with stability)
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Liaison
Note: This may step on the territory of the Councilor
Interacts with craftspeople and manages market-based foreign relations and trade routes
Benefit -Increase economy by Liasion's CHA or INT.
Vacancy Penalty- Decrease economy by 4.
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High Druid
Note: This may step on the territory of the Marshal or Grand Diplomat
Manages relations with fey and plants and animals. Agriculturalist. Also manages the castle's animal-life. May also serve as a falconer/game warden.
Benefit -Increase economy by 1/2 WIS or CON
-1/2 cost logging and farms
Vacancy Penalty- Decrease economy by 2, stability by 2. More animal/fey unrest
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Royal Chronicler
Note: This may step on the territory of the Spymaster or Councilor
The Royal Chronicler or archivist conducts propoganda for the empire, developing flags, national animals, and working with the Councilor to brainstorm appropriate festivals.
She also conducts research into old things and historical background of both the leaders and the land, to ground it in a strong history and to provide it with a sense of pride.
Benefit: Increase Loyalty by 1/2 CHA or INT
-Loyalty bonus an extra +1 for each festival level on the chart
Vacancy Penalty: Decrease Stability by 2, Loyalty by 2.