A player with a Dragonborn PC recently requested that he be allowed to grow wings and gain a fly speed in our game. I didn't really like any of the alternate Dragonborn options that allow flight, so here is my current idea. Is this option balanced with respect to the Dragonborn as found in the PHB, with the following feature replacing the Breath Weapon feature. (Leaving the Resistance intact.)
Draconic Ancestry (Alternate): Due to your heritage, your character sprouts wings and a tail that continue to grow slowly throughout your life. If wings are chosen at 1st level, you forfeit your standard breath weapon ability as your magical bloodline instead slowly increases your flight and mobility.
1st level: Wings and tail sprout from buds on your body, and slowly grow as you age. No flight is possible at this stage, as the wings and tail are small and frail (easily concealed under normal clothing)
3rd level: Your wings have grown as long as your arms, your tail is 1/2 your arm length and must be free to balance and maneuver if flying. Your wings and tail are no longer concealable, and you must spend +20% base cost to alter any clothing or armor you wear. You gain flying speed equal to your normal walking speed. Flying is extremely tiring at this stage, you may only fly for a number of rounds equal to 1 plus your constitution modifier (min 0) per short or long rest. If you are still aloft when this limit is met, you immediately descend to the ground, and have disadvantage on any attacks or skill checks made this round. You gain "Wrym's Charge": Your wings propel you to greater speed as you charge to attack an opponent. Your land speed while using this ability is x1.5 your base, but you must move in a straight line. If you charge in this fashion for at least 20', you gain advantage on your next attack roll. This ability recharges on a long rest.
6th level: Your wings have grown to equal your height, and your tail is 1/2 your height. Your flying speed increases to x1.5 your base speed. You may fly for a number of rounds equal to 1/2 your CON score (rounded up) per short or long rest.
Wrym's Charge is usable x2 per long rest.
11th level: Your wings grow to 1.5 times your height, and your tail is equal to your height. Your flying speed increases to x2 your base speed. You are able to fly for a number of rounds equal to your CON score per short or long rest. Wrym's Charge is usable x3 per long rest. You gain the "Flyby" ability (do not provoke an attack of opportunity when flying out of an enemy's reach)
16th level: Your wings and tail do not increase much in size, but grow stronger and thicker. Flying speed increases to x3 your base speed, you can fly for a total number of rounds equal to twice your CON score per short or long rest.