This is one of those "just for the heck of it" alternative rules whose intent is to add some fun and perhaps a touch of additional tactical complexity to the game. I designated this the Rabble rule, just to distinquish this variant from the Hordes troop elements provided for in DBM, about which I am largely ignorant.
What this rule seeks to simulate is the practice of some ancient and medieval commanders to enlist every available combatant (willing or otherwise) to bulk up their armies, including untrained levy, slaves, prisoners of war, old men and young boys, and men impressed into service. These troops would have been untrained and largely undisciplined, poorly armed, most often without benefit of armor or shield, and typically of low morale. In one word, a Rabble.
In a game in which the Rabble rule is in effect, players may elect before deployment to exchange one element from their normal list for a number of Rabble elements equal to the exchanged element's highest close combat factor. For example, you could exchange one element of Blades for five elements of Rabble or one element of Light Horse for two elements of Rabble.
If you wish to go to the trouble of modeling them, Rabble elements should be depicted on 40mm by 20mm (15mm scale) bases with four appropriate figures per element. Otherwise, spare Auxilia, Warband or Psiloi elements on similar sized bases can be pressed into service with an obvious marker to designate their "Rabble" status.
Rabble move at 200p off-road or 300p on-road. They have a close combat modifier of +1 versus foot and mounted. If engaged in combat or by distance shooting by an opponent whose total is more than the Rabble's, but not twice the amount, the Rabble will flee 600p. If the opponent's total is twice or more, then the Rabble is destroyed. Rabble have no quick kill capability against any opponent except Scythed Chariots, which is destroyed if its combat outcome total is less than that of the Rabble, but more than half.
No friendly troops may support or interpenetrate Rabble. Mounted troops (including Chariots and Elephants) may "ride-down" their own Rabble, destroying them in the process of interpenetrating them.
Individual Rabble elements lost in combat contribute fractionally to the victory conditions, i.e., all Rabble elements must be destroyed to count as a single lost element. For example, if an element of Cavalry is exchanged for three Rabble elements, then all three Rabble elements must be destroyed to count as one regular element lost.
In conclusion, I hope you have fun Rabble-rousing. Please let me know how they work along with any suggestions on fine-tuning this variant rule.