I have been testing the Tower Elephant and the (general) blacksmith upgrades.
It turns out the Archers and Crossbowmen on top of the elephant do not benefit from the upgrades. This means a regular crossbow will deal 18+11(vs heavy) damage, while the crossbow on the elephant will deal 15+11(vs heavy) damage.
The melee attack of the elephants gets the upgrades.
Is this a bug or intended? Because it does not seem intuitive the way it is right now…