If you're going to specialize any monster, specializ your dragons.
In my game, beyond specializing each dragon with unique abilities, spells, and other features, I allow the dragons to be extremely talented with their breath weapons. I allow them to use them in straffing runs when they fly which allows them to alter the shape of their breath weapon. A line can be a narrow cone, a cone can be made into a circular area. etc... I picture the dragon flying, and then allow the mental picture of what the dragon is doing and the mental picture of the breath weapon combine to create the inspiration for the game mechanics.