I'm hypothesizing Dragons that could have had their own natural path of development. This requires a series of pertinent mutations and capabilities that eventually overlap.
The first mutation causes alcohol to be selectively excreted as a defensive or emergency cooling method for "lizards" living in a desert climate.
The second development allows the creatures to spit this excretion. Then they develop the ability to ignite the expectorant. Like an octopus with its ink cloud, the flaming material distracts the predator, allowing the lizard/dragon to escape.
Flight is an almost secondary development, requiring a path from gliding, as some lizards do, to powered flight using a combination of fiery exudation and rapid noisy departure, like a grouse exploding from the underbrush.
Eventually, the dragons gain advantage through these modifications, and go from being the hunted to being a predatory hunter.
After many hundreds of thousands of years, they would become established at the top of the food chain, and have only each other as competitors. Some biological historians suggest that it is at this point a species begins developing the larger brain required to cope with social activities.
(However, I will take your suggestions under advisement for a time when "Dragons" may control their own development.)