Some good ideas. It should be reasonably straightforward to add in code that reduces civ hostility based on:

1. IED disarm
2. Building a fortification / well / something
3. Placing an AI group in the village on patrol
4. Clearing CQB positions
5. Destroying roadblocks (needs a destruct/delete mechanic)
6. Positive civilian interaction (where is Spyder's addon!?)

New:

1. Picking up anti-personnel mines
2. Removing UXO
3. IDAP resupply of assets in village/town
4. IDAP personnel placed in village/town
5. Establish IDAP medical tents.
6. Dropping friendly leaflets
7. Displays of force (low flight over civ areas with enemy presence)

Increasing civ hostility:

1. Killing civs
2. Destroying civ buildings
3. Negative civ interaction
4. Insurgent installation established in area
5. IED / Roadblocks

New:

1. Removal of IDAP assets
2. Destruction of medical tents
3. Killing IDAP folks
4. Dropping cluster bombs near civs
5. Enemy OPCOM dropping leaflets

As for Civ behaviour - the civ pop system today very much supports managing their behaviour, so its not a stretch to do the following:

Civ hostility low:

1. Crowds / Individuals exit buildings to welcome player groups as they approach town, with anims to wave, salute - might need some ambient crowd sounds such as cheering, clapping etc.
2. Individuals offer intel on enemy.
3. Civs spend more time outside
4. Civs form groups outside conversing
5. Civs request players to attack enemy positions/groups etc

Civ hostility high:

1. Civs throwing stones.
2. Civs jeering.
3. Civs staying in houses
4. Civs avoiding friendlies
5. No intel
6. Civs share player positions with enemy / call for enemy to attack

Just need a developer to pick this up! ;)