I mean, for someone who really wanted to go all-in, make the genetic parts of Dragonmarks a gift and the rest of the House aspects Culture. Then, as a player, pick both the relevant gift and culture, and you are now in as deep as you can get.
To use BSG terms, wasn't she pretty strongly hinted at being an advanced* skinjob type warforge with her "parents" having been part of the original team unraveling the mysteries of creation forges? I can't remember her name but am pretty sure Keith has given reasons to think of it being a possability that was more than just mere hint in some of his blogposts/potcasts.
The dragonmarks themselves are semi-genetic (it's not a given that a child will have a mark even if one or both parents do, but it's likely), and provide the actual magical abilities. The dragonmarked Houses are essentially megacorps/guilds who have formed around those family lines that often possess marks, and who leverage the advantages of the marks into dominating that particular industry. One can be a member of a House without having a mark, in which case you are either doing support stuff or things that are within the House's wheelhouse without requiring an actual mark (e.g. a House of Sivis scribe that only deals with mundane documents, not speaking stones or arcane marks), and one can have a mark without being a member of a House (either because someone's been sowing wild oats, or because you've left the House for some reason).
I would create a Dragonmarked culture that's generic, like the Noble culture. You were raised in a Dragonmarked House and learned the ins-and-outs of it. It may even involve gaining a cantrip or free skill specialty to show an innate ability (which depends on your Mark). In Eberron, IIRC, however, only a percentage of people born into a Dragonmarked House actually have a mark--and sometimes, illegitimate children (or grandchildren, or great-grandchildren) born outside the House end up with a mark.
