Realistically, you could handle both options by simply making more heritage feats; some for all classes and some for very specific classes. For example:
Fire Resistance/Immunity could be useful for all classes. Make a feat for it, and people who want it will take it.
Fire Breath could be useful to casters who want to focus less on their blasting spells, but still have an outlet for blasting. It also opens up blasting to non-casters as well. Again, make a feat for it, and people who want it will take it.
Dragon Claws obviously would have less appeal to those who aren't normally in melee. So, a feat like this would really only be used by some characters. A sorcerer could take it, but he probably doesn't want to be that close to the ogre in the first place.
Fire Mastery might only be useful to people casting spells with the [FIRE] descriptor, so it would be utterly useless to a non-caster, but a caster with a few [FIRE] spells might find it handy.
So, basically, keep the heritage feats relatively broad, then all PCs have a reason to take heritage feats. That way, you don't have to be a sorcerer to gain a mechanical benefit from having your great grandfather be a red dragon.
