Actually, some mechanism for auxillary attacks could be a most excellent thing, as it would also make same spot retinues for heroes moddable.
To be somewhat more balanced, a dude on a warhorse could first land his own attack, and then his horses attack.
Example: Sir Smashsalot the Gilden Sovereign on his trusted warhorse attacks a bunch of darkling warriors. Sir Smashalot first hits with his hammer (attack of 14), doing 11 damage vs the darklings 3 defence. Now his horse hits with its attack of 10, the darklings 3 defence is against factored in and hurts for about 7. The horse would be quite important against weakly armoured targets, but not do much against a Golem.
This would also help to bring fast lightly armoured troops better in line. Leather armour can get hurt by horses, plate cant, meaning that plate becomes more competetive.
One could also add some buyable "Squire" auxillarys (for Altar?), that add singular extra attacks to heroes.