Taking more damage from anti-cav units would be extremely convoluted. Bonus damage is determined by the unit dealing damage, not the unit receiving it. Negative resistance is probably the simplest way to increase damage recieved.
Mmm, yea the specific damage amp is more of an AOE2/4 thing. Prolly to complicated to port over to AOE3. That said general negative resistance would hurt the more fragile cav (ulhans, cossaks) disproportionately. Messing with durabilty of cav can be pretty unstable.
How bout this:
- No penalties to damage/recoil.
- trample mode causes cav to do splash damage once every so often as opposed to with every attack.