(This is totally too long, but I just kept adding ideas.)
Sometimes I play the game for like 15 minutes, find something I want changed, write a mod, then test, for a few hours every now and again. Been on the same run for like a month because of that.
One small thing I wrote is a call-to-arms kind of mod where Christian rulers ask nearby co-religionists for aid against the infidel if they come under attack. Now the French don't necessarily have to defend against the Moors alone, same goes for Navarra and the like in Hispania.
I also included the Pope in that but Paradox has now done the same better in Holy Fury.
Other thing I did was I drastically increased the popularity of backing a Claimant through a Faction when the Claimant is the brother of the current King or Emperor title holder and the succession is the Turkic type/Muslim type. Mainly to challenge myself and have more trouble dealing with my brothers when ascending on the throne.
I thought it also makes it more like the real thing back in the day.
Wrote a simple event where Aztecs have a chance for a hidden combat event for capturing war captives.
Then yearly in an Aztec Empire or Kingdom those captives are sacrificed in a jubilee to honor and appease Xipe Totec. Loosely based on reality.
The war captives are handled as a variable to avoid creating characters just to then bump them off.
The amount of captives in battle captured is based on the commander's traits and ability.
Number of captives are broken into tiers and prestige doled out based on that.
Also another Aztec event where repeated losses in battles and general unpopularity and/or lunacy etc may cause the ruler to eventually get overthrown and sacrificed to the Gods due to his incompetence.
Then his heir takes over otherwise according to succession.
When a war is declared, as the Aztecs, you can choose to sacrifice courtiers or prisoners to seek the favor of the Gods.
Aztecs have an increased chance of having an immune system susceptible to European and Asian and African diseases but over the centuries their bodies will adapt and this chance will lessen.
Thought it more interesting where Old World, or New World to the Aztecs, diseases are more deadly to them.
Handled through an event adding hidden modifiers.
As the Aztecs, a decision to organize a "man hunt", a bit like in the movie Apocalypto. Take a prisoner out, give them a head start and then chase them down. No claims to reality with this one.
Your vassals and courtiers will then react accordingly if the target of the man hunt was a worthy one or not. You'll just lose prestige and opinion if choosing the lame or the old etc.
Neighboring weaker rulers may ask you for a 10 year mutual non-aggression pact. You may demand that they pay you before you agree to sign one. A slight thing giving at least a bit of an illusion of diplomacy between realms. Don't know how it would interface with Sway/Antagonize.
If an independent neighboring ruler of lower rank is your prisoner, and you are not at war with them, you may demand they become your vassal or tributary in exchange for their freedom. They may acquiesce or not.
Similarly, you can ask your tributary if they would like to become your actual vassal.
If a tributary declares a war against you to end suzerainty, if you win the war and they continue on as your tributary, you may send a punishment expedition to extract concessions.
Like just money or that they demilitarize for a time or that their insubordinate ruler gets imprisoned by you.
The ruler may try to flee your army though. You can then mill about in their capital or head back home if he isn't caught in a few months.
If Aztec, demand that your tributaries send you prisoners to sacrifice. If you're persuasive enough, and they have no prisoners, they may be scared enough to send their own relatives from court.
You can ask a neighboring more powerful realm to let you be their tributary, so you don't necessarily have to swear complete fealty.
A short event where sometimes the Court Jester or Skald may ask permission to ridicule either the realm's nobility or nearby rulers.
If he badly individually offends your vassals, that vassal may demand you imprison or execute the jokester. Or they may just get upset at you for allowing this insulting display.
Some more events to penalize being a lunatic ruler, such as gouging your own eyes out, demanding all children under 8 in the realm be put to death (and vassals having choises to comply or NOT),
cutting your own balls off and surviving as a Eunuch and so on. Chances of injury and death are high.
Another penalizing random event with a few outcomes where if you land incompetent relatives within the realm, their inabilities may get them made fun of and you as well in the process by the rest of the nobility, and peasantry even.
If you owe money to the Jews and are not Jewish yourself, you will need to pay interest bi-yearly.
The abilities of your Steward will influence the actual amount.
Periodically your more enthusiastic vassals may urge you to go to war if there hasn't been one in a while.
You may promise a war or rebuke those vassals.
If you promise a war, you better have one within the year or they'll be back hounding you over promises broken.
Then if you fail your promises again, these vassals may back Factions to overthrow you or join Factions to go independent.
Your lover can send you a love letter and you can write one back.
You may get asked to perform Charity and hear out a petitioner's plight. Different outcomes, can even sometimes hire them or maybe you were kind and years later their son pledges himself in your service due to your past kindness to his now deceased father. Or just have them sod off in the first place.
Added Famine which works like a disease but also increases the chances of other diseases striking a character suffering from famine. High population (read: non-tribal, non-nomadic, prosperous) places after a severe winter especially are at risk.
If your relative is Decadent and in your realm, you can ask your court Imam to talk some sense into him.
May work and he loses the Decadent trait, or not.
If you're a Devil worshipper you can place a Curse on a target to produce negative outcomes to that target like going blind or losing a son or vomiting or catching the Plague. Or maybe nothing much happens or they just feel like a bit of a sniffle coming on, and that's it.
You can visit another independent ruler within diplomatic range to discuss the possibility of an alliance or troops or monetary aid. They may agree or counter with lesser options like just a non-aggression pact.
A decision to try for a baby with your wife or concubine.
A decision to try and forge your claim to being Sayyid if Muslim. May backfire if you're decadent and halfway to being a kafir already.
As the East Roman/Byzantine Emperor you have the option of holding Chariot races and betting on the outcome and also having your own sponsored Charioteer take part. Also nearby other friendly enough neighboring rulers may send their own Charioteers and bet on the victor. Need to hold Constantinople due to the Hippodrome located there to organize races.
Disabled excommunication by the game and wrote my own events, and extended that to Sunni Islam in the form of a Caliphal Fatwa.
The Pope may first just warn you and require a donation or some such, unless you're openly the Devil's kith and kin.
But I guess the Pope is more or less fixed in 3.0.1 now so this is kinda obsolete.
I've also released a few actual mods, but I cannot find those threads on the forums anymore, they are not in my Profile, at least I don't know where if so.
