I think this looks alright. It certainly doesn't strike me as overpowered, unless I've missed something. It does rather feel like a spell-less extension of DD into a full base class, which is certainly desirable. I suppose you might change the HD to d12 just to stay true to the DD and general draconic heritage. Though I think the BAB and the weak Ref save work fine; this isn't a class for dragons, after all, but for draconically inclined warriors. I don't think you need to keep the caster level halved for the SLAs, as they're not too powerful. I'm not sure if the ability score increases are balanced, though they don't seem excessive to me. I do rather miss them not gaining a tail slap and two wing attacks as opposed to the wing buffet they have now, though possibly that'd give 'em too many attacks.
Overall I like it and I think it works, though I never really cared for DD's flavor personally. But that's a personal thing. Lots of people wanna be able to play Dragon Warriors.
I might give this a more thorough look later; it usually takes me a while to wrap my head around the balance of a class, so these observations are just preliminary for now.
Well, it is a pathfinder conceit that 3/4 bab classes have a d8 hit die rather than a d10. I would compensate for this by giving this class a +2 to con earlier and maybe even more often. I would also kick in an extra +2 to strength somewhere so you actually end up approximating full base attack bonus (your BAB is 5 lower but your strength ends up 5 higher). I am a little worried about the level 1 +2 to charisma. I would maybe put that off until a little later to make the class less dip-able.
Also this is in the list of effects of dragon form:
"-1 AC, -1 Attack,"
Is this in addition to -2 to AC and attack from being huge?
I think you can afford to step up the damage on some of these abilities. I think the damage from the breath attack could stand to be your level in d6 and the breath weapon from your dragon form should just use the normal damage. I mean: plenty of classes can wear armor and produce blasts for d6/level damage. I would go ahead and hand that over to this guy too.
I think the usefulness of the level 8 size increase is pretty questionable. That is decreased accuracy with no stat boosts to offset things. And it also mean that your character can not go into certain places that the rest of the party can. Instead, I think you should give the class enlarge person as a spell-like ability a certain number of times per day (like 3+cha uses a day). And let her caste the spell on herself as a swift action at the cost of two charges. I am going to call that better.
After that stuff, I think you will be looking at a pretty good and interesting class.
A lot of fun ideas in this class, but the execution is a little messy. If what I understood from reading your class outline is correct, you are building a class for humanoids (I am assuming) that allows them to slowly transform into a single type of dragon.
While classes and races typically stay separate (sorcerer bloodlines being a notable exception), I would approach the class as granting a player the ability to slowly shift aspects of themselves into a more draconic likeness. I would avoid adding a lot of ability adjustments to avoid the aforementioned dips in the class just for the bonuses to Charisma and Strength.
The breath weapon is a good bread and butter ability that could be used at will (but I would keep the recharge time of 1d4 rounds) to give a ranged option to an otherwise melee centered class. The ability to manifest natural weapons (that can be dismissed) at will and the ability to grow leathery wings (look to the dragon bloodline for mechanic inspiration) for limited (and later continuous) flight would work too.
Sprinkle some draconic immunity and resistance along the way and give them access to a "wild shape" ability that uses form of the dragon spells as its base and at 20th level you could throw them unlimited use of their breath weapon (with the 1d4 round waiting period) and the unlimited use of their ability to transform into a dragon.
I would avoid changing the base character's size as a natural course of the progression. I agree with bumping up the HD or the BAB and maybe the skills if this class is going to specialize and try to be more dragon-like.
Otherwise I think you are on the right track.