Stupidity: Units with the 'stupid' promotion have a 5% chance every turn of gaining the 'suffering from stupidity' promotion which: makes them unnable to attack, only able to defend and (possibly?) cause them to randomly move (probably not as its not fun). 'suffering from stupidity' has a 80% chance of wearing off each turn, is lost after combat.
Having a small chance per turn of standing around in a daze sounds fine; in FF, we can use a Stupid promotion with
# <iPromotionRandomApplyChance> - Controls the probability of the promotion listed in PromotionRandomApply (Fair Winds, Enraged) being applied each turn
# <iPromotionRandomApplyChance> - Percent Chance per turn that the promotion listed in RandomApply will actually be applied
to give 5% chance per turn of granting temporary Dazed effect promo with the above effects.
Fear/Terror/Panic
The core mechanic in WH is that units combating a Feared enemy have a chance to panic and rout in terror, fleeing the battlefield and becoming extremely vulnerable to attack from the rear. Adding yet another vanilla bump to overall Strength is just not that satisfying or interesting for gameplay, it becomes effectively just another Iron Weapons or Combat I. Using a small chance of unable to attack and getting the scatter effect is a good suggestion. We could keep it simple, flavorful, and non-paralyzing by having a small (10%) chance when attacking a Feared enemy to instead panic and gain the Routed promo as below.
Routed: 0 moves, -50% defense, no First Strikes, 80% chance of wearing off per turn.
Units with Terror increase the chance of being Routed to 35%, or whatever playtests well. The base chance of Fear/Terror could be modified by a drastically simplified Leadership as below.
Leadership:
Yeah its really not worth trying to implement a complex 1-10 python system; but we could get the gist of the brave and cowardly units in WH with a few simple promos representing units that have relatively greater or lower leadership/cohesion.
Cowardly: Double chance to be Routed on Fear and Terror checks. +5% Withdrawal Chance. (Skaven and Goblins start with this.)
Brave: Immune to Fear, half chance to be routed on Terror checks. (Bretonnian knights, other elite units, etc). Could be purchasable with experience as well as a free promo for appropriate units.
Stubborn: -100% withdrawal chance, immune to Fear and Terror checks. (Ogres, Trolls, etc)
Then we could easily have Hero leadership effects in the vein of WH Heroes like we'd already planned; Commander effects that grant temporary Promotions like Brave to nearby units under their command.
Racial Hatred/Fear
As far as strategic-level Civ4 gameplay I agree with Ahriman that having a permanent significant strength advantage between races would prob just be frustrating for the player. We could keep it playable/flavorful by using the above Fear check (or immunity for Hatred, with a very limited strength bonus.)
Racial Hatred (eg, Hates Elves) : In combat with Elves, has +5% Strength, -100% Withdrawal chance, Immune to Psychology
Racial Fear (eg, Fears Elves) : In combat with Elves, make Fear check when attacking or be Routed as above.
Frenzy:
we can use the Enraged effect from Fall Further, and tweak as needed with playtesting.