On the road at the moment so can't check my books but from memory I only recall Skilled which gets you +3 proficiencies.
I don't have the statistical talent to be confident on the power creep merits of advantage vs bonus proficiencies, I just have a gut feeling that the inherent unreliability of advantage (it will often work but not always) and preserves the dominance/balance(?) of classes where extra proficiencies are a feature. That it only applies on active checks is also a limiter.
On on other points (apologies for lack of quotes, my update via phone skills are lacking)...
The more I think about it Investigation feels like a better fit for Medani than Perception, especially since I agree that skill already seems like the most used skill in the game. Not sure how to differentiate from Tharashk then though, except by swapping them to Perception as suggested.
Well, giving it some more thought, you do use Survival to track, so as long as you make it explicit clear they can use it in any environment, including urban ones, it could work. Either one, really.
A thing I think we may be missing here is the potential to give proficiency in a set of tasks, rather than a skill, as such. Bc technically 5e runs on ability checks. So, you might have bonus to Wisdom checks to find hidden things, or missing people, for instance. Or on Intelligence checks to work a portal, operate Lightning Rail controls, or examine or repair those devices.
Then proficiency or advantage both work quite well without stepping on any toes.
Side note, though. Giving proficiency as part of a feat or other feature wouldn't step on the toes of skill monkey classes, because a rogue with the feature still has vastly more proficencies than a fighter, and has expertise. And could probably gain expertise in the skill or tool or task, on top of that. Showing that a more skillful Cannith Heir will still be better at making magical stuff than a less generally skillful Heir with the same power of Dragonmark.
But, OTOH, Advantage lets the game show the same thing, so it's no big deal either way.
also, about converting dragon related adventure bits. I think as long as the thing doesn't require a cohesive giantish nation, it's probably fine. A small group of Giants using ancient rediscovered giantish technology fits really well. And brings Argonessen in as a faction you might work for, from a whole new angle.
[MENTION=57112]Gradine[/MENTION] I'd give Sivis scribing tools and 1 or more language.
Cannith: is guess that most Dragonmarked Cannith crafters *are* magewrights, artificers, or something similar. They are the #1 source for everyday magic items, from the prosaic stuff like automated brooms, to the eternal wands, to the charmed toys rich people get their kids, to magical plumbing systems, to carts that float. I'd go with Arcana and a set of Artisan tools, for that reason. But also see my comments above about using Ability Checks and *tasks*, rather than skills as such.
Orien: What about Wis checks to navigate, plus checks to examine, repair, and operate Orien Teleportation Circles and Lightning Rail trains? Then again, the couriers. Doesn't help them at all. Maybe they deserve their own background or subclass? Maybe Orien chooses from either Nav and dealing with circles, or Nav and DEX checks to overcome difficult terrain or clear obstacles without slowing (ie parkour)? Don't want them to duplicate Lyrander.
Lyrander: I like it. That works. But what about air and sea vehicles?
Mark Of Shadow: I think that works fine, but musical instruments aren't nearly as useful as disguise kits, so maybe two instruments?
Anyway, I think a lot of House stuff can be covered with backgrounds, as well, especially since many non marked members of the houses still specialize in certain jobs the house is known for. Not all Medani Inquisitives or Tharashk Finders or Cannith Artificers are dragonmarked. Some may benefit the game as subclasses or feats, as well.
