I am not so sure about adding trebuchets to the game. Siege weapons like trebuchets were apparently phased out around the mid-15th century in favour of gunpowder weapons, therefore adding them to the game would be very out of place.
However, a unit armed with a staff sling could possibly make an appearance in the game. The staff sling is described for being a handheld catapult or grenade launcher which was used for throwing grenades well into the age of gunpowder.
Maybe there could be an historical battle for the French that features the Couillard, which was a type of a trebuchet developed by the French that has a split or two counterweights. The Couillard did apparently continue to be a practical weapon well into the 15th century and even into the 16th century.
The name for this siege weapon is also funny since “Couillard” means “A man’s nuts” in old French (I’m not kidding). I couldn’t include the specific word for said body part in this post due to censoring, so I settled with the closest meaning to the word that wouldn’t get censored.
The image below shows a late Roman or Byzantine soldier armed with a staff sling.
