Qm said

[Zath]

The training of war horses and elephants have historically been focused on suppressing the natural instincts of these animals to flee when struck by weapons or startled by noise and large crowds. Training an animal to trample opponents is especially difficult, since they must charge through what they perceive as solid obstacles. All the above factors can be modeled in game with a similar mechanism to repel: force tramplers to pass a morale check for each square they trample, and make them attack with their normal weapon if they fail this check. The difficulty of this morale check can be adjusted based on any number of factors that the designers find suitable. For example, the mechanism could be setup as:

Trample Roll = Morale - 1 per every 20% HP loss on unit
Fear Roll = 5 + 1 per every 6 hostile size points in adjacent squares

If Trample Roll > Fear Roll, then trampling succeeds, otherwise attack with normal weapon and end turn. What qualifies as "adjacent squares" must be further defined of course, but just using the 8 immediately adjacent squares may well suffice. A system like this would make some roleplaying sense, and it should mitigate the problem of trampling rushers without completely negating the effectiveness of these units in a combined arms battle. Swarms of cheap infantry could be used to freeze tramplers in place and whittle them down slowly. This can be countered by using archers or shock infantry to cut through the chaff, which will in turn be vulnerable to other counter-counters, etc. etc.