Well, it would motivate infantry players to shoot horses with their throwings or atleast set a trap for cavalries before/during teamfight. While playing normal skirmish or pickups, no one cares about enemy cavalries. When i am waiting for enemy cavalries to dismount them with my throwings or spear and succeding to dismount them I gain 0 score. Dismounting heavy cavalry horses should give 125 score, assisting for dismount should give 50/75. Dismounting light horse should give 100, assisting dismounting horse should give 50 score. So finally, maybe players start focussing enemy horses