Next FE should have a manakete as one of the main heroines. Make it so they function entirely different from normal units and consume a resource (like energy/stamina) to attack and have a bunch of different attacks that have specific niches to pick from, like breaths, claws, bites, tail swipes, etc. You can't recharge the resource and it limits how many combats they can do per map, but fully recharges every map.
Personal preferance unrelated to gameplay, but I hope she has some of her dragon features out in human form, like wings, horns, tail, etc.