Another ambitious suggestion is adding Unit Traits
Unit Traits
Each unit created starts off with one random trait. These traits are mostly positive but minor, but some have moderately stronger effects with drawbacks for balance. Even civilian units (such as specialist units, workers, missionaries, and settlers) have their own list of traits. These promotions are added to the unit's custom name.
These vary, including but not limited to:
Military Traits
- Light (+5% withdraw chance)
- Heavy (+5% )
- Quick (-10% , +1 movement)
- Brutish (+10% , +1 movement penalty)
- Attacker (+1 for attacking, -2 to defending)
- Defender (+1 for defending, -2 to attacking)
- Mentor (when defeated, gives a portion of XP to a random other unit)
- Patriot (+20% within national borders)
- Cunning (10% chance to survive being defeated, and relocate to the nearest city)
- Defender (x2 benefit from defensive bonuses)
- Raider (x2 gained on raid)
- Champion (+20% XP gained, +50% upgrade cost)
- Militia (-20% XP gained, -50% upgrade cost)
- Ambitious (+10% healing when in hostile territory, -10% when in friendly territory)
- Peacekeeper (+1 happiness in a city, enemies defeated give small amount of in nearest city)
- Conviction (5% chance an enemy unit defeated joins your civilization)
- Looter (10% chance for from a defeated enemy)
- Terrain-Expert (+5% on one terrain type, and -1 movement penalty in it)
- Siege-Breaker (defeating an enemy near a friendly city gives a small amount of , happiness, and )
- Inspiration (defeating an enemy near a friendly city gives based on era, and towards cultural buildings)
- Explorer (+1 visibility, higher chance for a good result on tribal villages).
Some buildings or wonders can determine the traits gained by the units built in that city.
Military (Siege) Traits
As general military, but includes the following:
- Poisoner of Cities (after bombarding a city, inflicts 1 for 2 turns; representing biological warfare throughout the ages),
- Terror of Towns (as ruthless, but unhappiness instead),
- Unmaker of Wonders (-10% withdraw chance, but a successful withdrawal after a city gives a small amount of ).
Military (Naval) Traits
As general military, but includes the following:
- Boarding Party (as conviction, but 10% chance against ships),
- Skeleton Crew (-10% Str, +1 unit capacity),
- Blocking Expert (gains a small amount of for each trade route blockaded),
- Blockade Runner (when attacking another naval unit that is blockade mode, gives +20% withdrawal chance. If successful, ends up in another square adjacent to the blockading unit with extra movement).
Military (Aerial) Traits
As general military, but includes the following:
- Airfield Bomber (deals extra damage when bombarding a city that has aerial units stationed inside),
- Dogfighting Expert (deals extra damage when intercepting),
- Keen Eye (deals extra damage to enemy units in difficult terrain)
- Expert Bomber (deals extra damage to enemy units in open terrain)
- Vigilant Pilot (+5% interception),
- Multitasker Plane (adds +1 commerce to the city stationed in)
- Overwatch Expert (adds +20% defense to the city stationed in)
Civilian (Includes spies, workers, settlers, missionaries) Traits
All civilian units gain 20% withdrawal chance to help boost their survivability.
- Industrious (workers have increased building speed, missionaries have higher success chance for spreading faith, other specialist units, as per the Non-Great People suggestion above, have higher success chance on their active missions)
- Cunning (10% chance to survive being defeated, and relocate to the nearest city)
- Swift (20% withdrawal speed, can evade capture or defeat by military units)
- Rash (+1 movement speed, -20% withdrawal speed)
- Hardy (+1 defensive strength, +1 per era)
Loyalty (Revolutionaries and Loyalists)
All units have a chance to also gain loyalty promotions.
There is one loyalty promotion for each civic and one for each religion. In effect, these are markers for revolutionaries and loyalists.
For example, a unit in a civilization that is Catholic and has the Monarchy and Mercantilism civics active has a chance of gaining Loyalty (Monarchy), Loyalty (Catholic), and Loyalty (Mercantilism).
Loyalty promotions determine the unit's fate during revolutions (when changing civics), great heresies (fancy name for changing religions), when bankrupt (are not disbanded when you are in the financial red), and when collapsing.
- When you change civics or religions, all units with the relevant loyalty promotion have a 50/50 chance of either becoming enemy combatants (independent), or leaving your civilization in disgust and joining another civilization with the civic or religion you abandoned (prioritizing nearby civs). When an enemy combatant, they do not attack other civics who share the same civic/religion, but can be attacked. They, naturally, keen their original name, so it might be cool to suddenly be gifted a diehard Monarchist veteran from Paris when your neighbor France is going through the Reign of Terror.
- When you go bankrupt, loyal troops do not get disbanded (although they are still counted for financial purposes), but they suffer a small demotion (-10% healing speed) to represent logistical difficulties when bankrupt.
- When collapsing, all loyalty units remain under your control, but do not automatically relocate to the nearest city that is friendly to you. They receive the ambitious trait, losing it when entering your territory, but giving a +1 happiness bonus for 2 rounds.
Naturally, adding this mechanic opens up the door for synergistic mechanics, such as one civilization having higher chance of attracting loyalists, or making all revolutionaries defect (but to nonhostile civs) instead of becoming hostile units.
To be honest this loyalty/revolutionary mechanic is the primary reason for this post, but random traits also adds a layer of depth to gameplay.