illager horsemen

patrols of illagers may spawn as horsemen groups rarely
illagers during raid may spawn as horsemen in some of later waves
melee illagers use iron spears instead of axes and try to ride against their targets like zombie horsemen do
ranged illagers keep crossbows and they try to keep distance if you get too close, using horse speed to their advantage
they all use higher than average stat horses players can keep and use for further breeding, horses may have iron armor
crossbow illagers may spawn with donkey rider with little of random illager loot as emeralds or food items in their chests as part of patrols
horses may spawn in cages of illager camps

those would add little extra challenge and diversity to illagers met around, tie them to mounts update, would make sense regarding illagers being militaristic group, add reward (if kept alive) in form of better than average horses, easing up horse breeding or giving average player better average horses to play without need to engage with breeding if they dont intend to get really superior horses