Again, I appreciate the advice, guys. I think you're right about me "Springer-ing" / "RHing" Dennis' backstory. (Perhaps I've been behind the screen too long; I'd forgotten that personal history and personality are all that a player really has.) I honestly don't think Dennis would have a problem, but, *Sigh* I also feel like a bit of a D-Bag for even considering it.
Having had time to sleep on it, I've concluded I'm willing to allow this. I came upon the following realization:
Since, in common usage, "Goblin" can mean
- Goblin;
- Hobgoblin; or
- Bugbear;
Perhaps, in common usage, "Elf" can mean
- Wood Elf (Elf);
- High Elf (Eladrin); or
- Dark Elf (Drow)
Thus, perhaps the "Elf" in "Half-Elf" refers to the common usage of the word. I'll likely say that since "Elves" are the most common "Elves" in civilized parts of the world, most Half-Elves will still be of Human and Elven parentage, but this still leaves the door open for me to let PCs be of more unique parentage.
I also intend to use the tool I consider to be the real "DM's Best Friend": Communication with my players. I'll sit down with Dennis and say,
"
Look, I don't know if you were serious about being 'Half-Eladrin' before. Are you serious? If you are, here's what we can do."
- I'll ask him if he'd like to change any of his physical features to appear slightly more "Eladrin".
- I'll tell him that for his Dual Heritage race feature, instead of being able to choose from both Human and Elf feats, he can choose from both Human and Eladrin feats. [DM's Note: Not sure if this will have any unbalancing effect, but my preliminary estimation says it shouldn't.]
- I'll tell him that, other than the above, his race will follow the same details described under the "Half-Elf" entry in the PH, in terms of both mechanics and flavour, with the word 'Eladrin' substituted for 'Elf' where appropriate. [DM's Note: I don't really see why anything else in there would need to change. Perhaps the languages for Half-Drow, and that's it.]
- Finally, I'll tell him that all of this may be subject to change, at our mutual discretion, should "Half-Eladrin" ever receive an official treatment.
Problem solved? I think so.
One last thing: Would it still be as "douche-y" a move to include a story arc where Dennis' character questions his heritage after meeting an Elf man who claims to be his real father? OTOH, I'm not running a soap-opera. (For the record, I am no longer seriously considering this.)
Would you guys ever do it?