Edit MrT: Marker for Johan
What about randomizing the chances that claims are passed down? Adding the random chance claims aren't passed down could simulate any number of historical possibilities: lost/stolen/destroyed documents, behind the scenes treaties, blackmail, intersibling rivalry, etc...
If claim inheritance could be scripted as an event that triggers on the death of a claimholder, this might work. Plus, this would make it easier to tweak variables.
Suggested factors:
1. Importance of Title: The more important the title should mean the more likely the claim is passed down. claimants would be more concerned about a claim to the throne of England as opposed to the county seat of Somerset.
This could be coded as a base value: King - 1.0, Duke 0.9, Count 0.8
2. Rank of Claimant: Logically, random untitled courtiers would cling to the hope that they would inherit the crown of some faraway land much more than a noble who already had his own titles and court. Plus, kings tend to accumulate the claims on so many lands that it becomes cumbersome reading through the messages by the end of the game.
A modifier based on the highest level of title held by the potential claimant could be: King - 0.8, Duke - 0.9, Count - 1.0, None (plain old courtier) - 1.1
3. Intrigue of Claimant: It isn't too much of a stretch to assume that characters with high Intrigue scores would be scheming as much as possible to ensure existing family claims are upheld.
This modifier could look like: Intrigue >15 - 1.5, Intrigue 12-14 - 1.3, Intrigue 10-11 - 1.2, Intrigue 9 - 1.1, Intrigue 8 - 1.0, Intrigue 7 - 0.95, Intrigue 6 - .9, Intrigue 5 - .8, Intrigue 3-4 - .7, Intrigue <3 - .5
4. Piety: As a claimant is held in higher regard by the church, the church should be more likely to recognize and validate his claims.
This could be expressed as: Piety >500 - 1.5, Piety 250 to 499 - 1.3, Piety 100 to 249 - 1.1, Piety 1 to 99 - 1.0, Piety -99 to 0 - .9, Piety <-99 - .75
5. Character Traits: Certain claimant traits lend themselves to this formula, such as: Selfish - 1.25, Modest .8, Energetic - 1.05, Wise - 1.05, Bastard - .5, Arbitrary - 1.1, Honest - .9, Generous - .9
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Using this formula, a thickheaded king who has run afoul of the church would only have a 24% chance of inheriting any count-level claims from his father. Contrarily, the very clever and pious son of the deposed King of Spanish Galica (now residing as a courtier in the Duchy of Spanish Marche) would have a 247.5% chance of keeping the claim to his father's old throne alive.
It favors players (and the AI) playing counts to keep their claims, but prevents kings from stockpiling too many claims.