The title's a bit misleading but it's the best way I thought of to lead my question:
A friend of mine made a draconic bloodline sorcerer, and I went and mentioned to him all the other different types of dragons there were in 2e's other bestiaries since the first one, and he got really hooked on Sovereign Dragons.
So he started asking me if he could make a sorcerer with a bloodline tied to a Sovereign Dragon. RAW says no, but there's also an argument to be made that the draconic bloodline sorcerer was written at a time when Primal and Imperial dragons weren't added to the bestiary yet. Adding to the point, the Wyrmblessed Bloodline does include Primal and Imperial dragons into its listed of possible draconic lineages, so it's wholly believable to me that the draconic sorcerer description just hasn't been updated to include the complete list of possible dragon options, either because for the sake of keeping the same page count or because nobody's mentioned it so they haven't circled back around to it.
Regardless of the reason behind it, is there anything stopping me from acting on this? Make his sorcerer an Occult caster since spellcasting Sovereign Dragon would be an Occult caster and make the damage type tied to his bloodline spells mental based off the Sovereign Dragon's breath weapon? Arguably this is more of a homebrew question, but the point of asking this in rules is to bring to light and hopefully get an answer on whether Draconic bloodline was meant to be applicable to all existing dragon types the same way that Wyrmblessed is. Maybe it'd still be arcane since Wyrmblessed is consistently divine regardless of the lineage, I dunno. Any input is appreciated.