Let’s come up with new “war machines.”

As suggested here, it would be better not to reinvent the wheel, but rather to slightly improve the old one. Therefore, let's create alternative upgrades for the siege weapons of each race, naturally, their appearance will now be different for each race:
1) Elves. The tent gains the "Swarm of Wasps" spell (it will look like a beehive; you can heal your own units or cast the spell on the enemy). The ballista gains a 15% chance to blind the target it shoots at. The cart should not receive an alternative upgrade at all.
2) Humans. The tent gains the ability to inspire. The ballista's damage is increased by the "Retribution" ability.
3) Demons. The tent can summon imps (the number depends on the skill in siege weapons). The ballista adds the "Fireball" spell to its damage.
4) Mages. The tent summons elementals. The ballista fires a magical arrow that pierces through targets, like mages.
5) Necromancers. The tent revives undead. The ballista casts the "Plague" spell.
6) Warlock. The tent casts antimagic on one of the units for three turns (once per battle). The ballista adds elemental damage to its damage.
Think of something for the Dwarves...