Preamble

So, obviously this is rather abnormal for classes in 5e so far, but given the raw power of older dragons and how clearly a dragon's power scales down and up with the different ages, it's easier than most creatures to adapt this way, and impossible to allow as a race.

Naturally, all dragons are usually both formidable melee combatants, and have powerful AoE effects only seen in spells in PCs.

So, even though some minor, uncommon mechanics don't line up with the general case, I'm using the Pact of the Blade Warlock as the base concept for the three more castery subclasses of dragon, and adapting a half-caster-ish version thereof for the two more mundane ones.

Obviously, level 1 PCs will not be fully powered dragons, but there should be enough of a base there to still feel like a dragon while everything builds up.

Now, everyone's first thought when they see this is: If someone's class is defining what species they are, then what're the race stat blocks?

All I'm going to say here is that, yes, I'm thinking about this and it actually plays a crucial role in the class's design.

I'm trying to aim at slightly underpowered, yet still viable, so that they can be carefully buffed up to scratch. Let me know how well I did on that.