This is the first article in a new series, which will have the tag "13A Options." 13th Age is a young game, and it has a streamlined, transparent, and flexible rules set that lends itself really well to houseruling and homebrewing. It embraces the philosophy of working with players to help them create the type of character that they want, but with just the core rulebook so far there's a lot of room for expansion. As a disclaimer, I'll say up front that I'm NOT hoping for a long line of splat-books and option-glut. D&D suffered horribly from that, I think that it ultimately detracted from the game.
These additional options are more along the lines of providing advice through examples on how you can go outside of the rules as written (RAW) to provide some interesting mechanics that back up your players' concepts.
So let's dig right in, then. The Half-Elf was given its own unique racial ability during the public playtest, and while its racial power "Surprising" does give the Half Elf its own identity outside of its two parent races, it suffers from the unfortunate consequence of being applicable to only a narrow range of classes. Given the strides that 13th Age otherwise took to ensure that any race could be viable with any class (ability bonus from both race and class, notably), this is a problem. I'd argue it's a big problem. While rolling up characters for playtesting I've always passed on the Half Elf, and none of my players have ever chosen one in a game I've run. My solution is an alternative racial power.
Special: You can choose this instead of Surprising when you create your character. When you make this choice, you also need to choose one Elven sub-race for your parentage.
Roll Initiative twice as if you had the Human's "Quick to Fight" racial power. If the second roll is lower than the first, you gain the power of the Elven sub-race that you chose for this battle.
Champion Feat: Once per day you can use your Elven power even if your second initiative roll was higher
Discussion on Balance
At first glance this might seem to be a but too powerful. After all, Humans don't get a "consolation prize" when their second roll is lower than their first! But Dual Heritage should be better than Quick to Fight, because a Half Elf doesn't get the bonus feat of a Human. And since you're only using the Elven power when the Initiative re-roll failed, you'll still never benefit from more than one racial power in a single battle.
This is pretty similar to the original racial power from the first Escalation Edition, "Adaptable." That power let you choose either the Human or Elven racial power when you roll Initiative. Dual Heritage is a little more streamlined in that it bypasses the possibility of option paralysis. Because it combines the two racial abilities into a single-trigger amalgam it also feels more like its own thing compared with "choose one of these two powers, use them exactly as written." I also like that it has an element of randomness to it, which reflects the wildness and the chaotic elements of a Human pairing with a Fey. What you get out of that union shouldn't be completely predictable. This notion is at least partially inspired by the art on p. 69 of the core rulebook.
I'm including this section to provide some insight into the design process of this power. Initially, I was thinking of wording it this way: "Roll Initiative twice as if you had the Human's "Quick to Fight" racial power. If the second roll is odd it doesn't count; instead you gain the power of the Elven sub-race that you chose for this battle."
This version came about after thinking about monster design and flexible attacks right after each other, so I obviously had "let the die roll be the trigger!" on my mind. It was also a really easy way to get 50/50 odds on whether you use the Human or Elven power while obviously preserving that element of uncertainty. The problem with this is that it's no fun for the player if their first Initiative roll is really low, and then they roll a 19 on the second die and don't even get to keep it. The current form is much more satisfying to a player. It feels cool to be able to say "I have the Human's power, but better!" without actually making the two races unbalanced.