Mercule
Adventurer
Nope. I think there should be a "House Scion" background that's somewhere between Guild Artisan and Noble, but that's a different matter. Dragonmarks are way too potent for a background.Wouldn't backgrounds be a better mechanic?
There are really only three ways I can see to do it:
1) DMO: Treat it like treasure and/or boons (I think that's what the DMG calls them). If you're willing to be unbalanced, just go ahead and admit you're winging it.

2) Feats: I built my own, but the UA versions are serviceable. If you don't like not having them manifest until 4th level, then either allow PCs to trade in their stat bonus (maybe let humans use the alt build and take the feat) or grant everyone a feat at first level. I chose the later, which makes the whole group more powerful, but that's Eberron's cinematic feel, right? FWIW, I implemented Action Points as an x/long rest (don't remember x) that counted as a feat; if the player wants the easy path, they just have action points.
3) New subsystem: Adding some sort of perk/flaw system would probably be the ideal, but takes a lot more work. It would also allow a variety of other tweaks. I envision it as a zero-sum system that can be easily ignored. The general pattern I've seen for these has been three tiers (minor/average/major) of both perks and flaws, but it could also be equated to a stat point buy value. Maybe a feat is an average perk worth 4 points. The player could just have 4 less stat points to spend, or take the Hunted flaw, which is also worth 4 points. A double dip in background might be a minor perk worth 2 points. That's all spitballing, but you get the idea. It's a dangerous path, though, because it makes D&D start to look like a character point or classless system, which it does not do well.