The neutral unit technically belonged to the "good" Order faction, but the unit's name clearly states - Evil Sorceress. And since they are so evil, they should be in the "evil" faction, especially since there was a precedent in the fifth part - remember the witches with whips? Let's just make them human.
The ram seems to me to be a slow plague, completely useless against low-level units... But how well it destroys high-level monsters and fortress walls! And what? The city needs to compensate for the lack of flying units.

If you apply a little imagination (scorpions are operated by cool mage-priests, they feed on faith and shoot with righteous light, for the ref - to the enchanted ballista of the tier 5 elves), then they are quite suitable even for high-level units.
My lineup in ascending order of strength: imp, cerberus, golem, dragon fly, slime, juggernaut, queen.
And instead of imps, you can try to make something very weak and very numerous, so that even the model is small and unimpressive. Flies, larvae, mosquitoes... But, as you rightly said, without extra limbs and growths, with a concise design. Make them have the largest number among the first-tier unit, cheap stats (1-2 hp, for example) and let them swarm. Various skills that give +1 hp to the unit and the like will be super effective, and with a certain upgrade, this tier will be a force.
Well, as promised, I will express my valuable opinion about the units, the lineups of the factions, and also share my own versions of the lineups.