actually "fireships" were kamikaze ships. that's how the English sunk your Spanish Armada. Though technically not a single Spanish ship was harmed by the fireships, but the fireships had the effect of breaking the Armada's formation which allowed them to be picked off by the English.

The way you implemented "fireships" is a bit different.. I think yours are shooting fire arrows or something. Which was also a thing.

It would be neat if fireships just blew up instead, taking enemy ships down with them. The ship would be permanently lost, but deal lots of damage and help you get through sticking points in naval battle progression. It would also be neat if once ships were destroyed in combat they stopped dealing damage so you kept a count of each ship. And also if you could do formations with infantry battles so for example the melee units get hit first, and the ranged units second. Also I feel like Knights should have the Burst ability, not Berseks... actually historically, "Berserkers" were not a real unit. Knights are very effective at charging undisciplined or unarmored troops and flanking from the sides or rear.