Dragon Shaman is really all about the auras. Without them, there's just not much left.
I'd think that mount advancement should be tied to character level -- special abilities that are suitable for a mount or familiar are not necessarily suitable for a PC.
So, you basically like the breath weapon, but not much else? Dragonfire Adept is a good thing to steal from -- drop Invocations, just grant Breath Effects, and let it wear armor. BAB matters a lot less than with a Warlock, since breath weapons don't require an attack roll -- so tailor its skills and other class benefits to the BAB you want to grant.
Cheers, -- N