First, I don't consider Hussar Dragoon or Cuirassier medieval. They were during 17th, 18th and 19th centuries. A bit late for medieval. A bit early for industrial (that's why in my mod the first era is ancient & medieval, and the second renaissance & imperialism.
Second, what is the difference :
- Hussar = light fast cavalry -> lower defense and attack, but +1 move. I give them ZOC (harrassment) and Blitz (they have a low attack, but they can use blitz to exploit weak points in the ennemy lines, and attack poor defender behind ennemy lines).
- Dragooon = mounted infantry. Medium attack and defense, but I give them defensive bombardment (= range of 0).
- Cuirrassier = shock cavalry, high attack value.
In my mod, all these different type of cavalry is available at the same time, with the same techs.