I, personally, am not opposed by having a Dragon being a permanent part of your army. I mean seriously ... whats the point of dragons if you can't own one at some time?
Personally I am against being able to ride a dragon, however I personally would want to be able to fight with my very own dragon, and have a dragon leading my armies.
One ... hatchling Dragon. Once you get the egg it takes 5 turns to hatch, and every year gains +1 HP, and every 5 years gains +1 Attack and Defense.
At 50 years of age, the hatchling "upgrades" to an Adolescent. This is a change of art, gains Flight and Dragon Breath abilities, gains +20 HP, and +5 attack, +5 defense. +30% movement speed (other than flying) And +1 combat speed. (for a total of 80 HP, 20 attack, 20 defense, 2 combat speed)
At 150 years of age, Adolescent "upgrades" to a Mature dragon with +50 HP, +5 attack, +5 defense, and +2 combat speed (and +20% movement) ... for a total of 230 HP, 45 attack, 45 defense, and 4 combat speed. (at this point attack and defense stop increasing)
at 500 years of age, Mature "upgrades" to an Ancient Dragon. At this point, the growing stops. It gets its final art change ... gets "Ultimate Dragons Breath", and "Unending flight", as well as +100 HP, +10 attack, +10 defense and +100 magic defense, and +50% magic resistance. For a grand total of 680 HP, 55 attack, 55 defense, 4 combat speed, 100 magic defense, 50 magic resistance, Unending Flight, and Ultimate Dragons Breath.
In addition, Dragons can level up, but it takes 5 times as much Exp, and they only get 5 points per level. (+5 HP, +0.5 attack, or +0.5 combat speed, ect)