Looks promising. Keenly following. I have not read everything in here, so apologies if I repeat suggestions others already proposed.
1.
Armoured Units & Morale. Friendly armoured vehicles boosts morale by being present. Closer vicinity equals stronger effect. Vice versa, enemy armoured vehicles hurts morale by being present. Closer vicinity = stronger effect.
2.
Armoured Units Destruction & Morale. Friendly armour destroyed hurts morale. Closer vicinity & witnessing the destruction / explosion / burning = stronger effect. Same mechanics but opposite effect regarding enemy armour.
3.
Witnessing gruesome gore & Morale. Witnessing particularly violent deaths of any kind (dismemberment especially) hurts morale. A bit if enemy, a lot if friendly. Vicinity gives stronger effect. Absolutely requires that the gore is witnessed ON SCREEN.
4.
Distance to friendlies & Morale. (I did read the OP on morale). Heavy penalty for being away from friendlies. Even a single friendly nearby helps combat the worst effects, but more regular soldiers have small effects beyond that. Squad members have a bit stronger effect. Squad leader and Commander have
huge effect. This is a realistic way to motivate others to integrate into their squad.
5.
Death of Squad Leader or Commander & Morale. Similar as tanks. A hefty (but temporary) morale shock, but depends on vicinity. The closer, the stronger the effect.
6.
Reload speed & Suppression & Morale. Reloads slower, or failed reloads (drops the magazine, puts the wrong magazine in (a bug presently often makes the player insert an almost empty magazine instead of one of the full ones regardless of morale/suppression state), has trouble getting the old one detached from the weapon, drops the cartridge when trying to feed them one by one into the opened receiver). I believe Far Cry 2, and Fallout: New Vegas, has some of these effects. In the latter, a weapon with lower condition sometimes requires extra effort to really work the bolt, put in a new mag and such.
7.
MG34 properly firing a mix of tracer and regular ball. In game, shooting semi-auto makes it shoot only non-tracer, while auto fire gives proper mixture. The HMG34 properly feeds the mixed ammunition during semi-auto.
8.
Taunts / war-cry & Morale. Hearing enemy taunting or charging with bayonet gives a morale penalty.
The closer the vicinity, the stronger the effect. The charge scream being scarier. Vice versa, friendly war cries & taunts give slight morale boost.
9.
New Ability: Rest MG without bipod. This simply permits shouldering the MG as a rifle with iron sights, on window frames and other objects. This is meant to get around the sometimes absurd situations where it can't be deployed properly (there are some positions, such as on Pavlov's House, the Axis corner apartment building, second floor eastward, with superb view down a street and Zeb's House, has sandbags and some curtains above it - MG cannot deploy). Or when it can't be pivoted down far enough to hit those 5 guys crawling close to your building etc. Fatigue when shouldered (more sway), sluggish response to movement (just like when manning HMG) and MKB-type recoil, with unstable lateral movement tendencies from recoil (imagine the barrel sliding on a window frame sideways, not being securely attached to the ground with the bipod the way it should be).
10.
Lock human crew at their crew position in tanks. If assigned as driver, unable to flip instantly between the other AI crewed positions. But is able to switch if another crew position is unmanned (crewmand died etc), which is a slow awesome looking animation inside the tank. The current situation with a friend in a P4 is often terribly chaotic, and rather gamey.
11.
Elevation & Morale. Being higher than enemy gives boost. Being lower gives penalty.
12.
Cover & Morale. Being behind sandbags, masonry stuff, trenches, gives morale boost. Being exposed in the open gives morale penalty.
13.
Location Memory Associations & Morale. Whenever seeing friendly wounded or killed, the location of this event is stored. Going close to the location of the
previous casualties gives a morale penalty. Typical example: Witness many people killed in a certain window, or trying to cross a dangerous street covered by enemy tank or MG fire. Going to the area where this happened (Maybe 5 meter horizontally, 1 meter vertically radius?) = morale penalty.
14.
Friendly Fire & Morale. Wounding a friendly = moderate morale penalty. Killing a friendly = severe morale penalty. Vicinity very important - such as guys who intentionally teamkill at 2 meters range with a shot to the head get the severest morale penalty possible, lasting until they respawn. Also, nearby casualties caused by friendly fire = higher morale penalty than if caused by enemy. Seeing casualties from friendly artillery for example, causing more morale penalty than if enemy artillery.
15.
Ammunition & Morale. When running low on ammunition (say 1-2 magazines/clips) a morale penalty occurs. The less ammo, the stronger the effect. Having no ammunition gives the strongest. Vice versa, being well stocked on ammo has a positive effect.
16.
Smoke & Tanks. Did they by any chance have means to deploy smoke screens to protect themselves? Modern vehicles all have advanced smoke tube launchers that are highly effective for that. It seems likely that the advantage of smoke was known in WW2 times. Even just throwing some grenades out the hatch while reversing could help.