The entire discussion surrounding this (in general, not specifically with you) has consistently sounded to me less like a legitimate push to allow for more diverse mixed ancestry representation and more like a way to quietly sweep them under the rug by making the option available, but completely irrelevant and largely invisible.
But, that's the thing. The two examples of mixed ancestry races that we have in the game already are largely superfluous. There's so little difference between the 2014 and the 2024 races that who really cares?
We talked about Dwarf/Dragonborn before. You describe it however you like. That we all agree on. Now, we're just talking about racial abilties. So, I describe a dwarf that is resistant to fire (random example) and has a fire breath weapon. How is that not a "Dwarfborn"? Or, I describe a short, stocky, scaley, horned character that is resistant to poison, can see in the dark and has extra HP. It's not a dragonborn. It's a "Dwarfborn".
The a la carte options simply won't be different enough from the parent races to actually matter, no matter what, because the racial abilties largely don't actually matter that much. Their impact is largely invisible.
What's your background?
I'm a scholar.
I'm a blacksmith.
I'm a noble.
I'm a half-elf.
I'd consider "mixed heritage" to be a very viable background. THAT'S where you plonk down some of the choices that aren't specifically tied to biology. You want your DwarfBorn to have a breathweapon and mason's tools? Poof, done.
So much of the stuff that's doubled up between races and background can be simply covered by background. Proficiencies, languages, skills, weapon proficiencies (which are typically doubled up by class anyway - who cares that you get axe proficiency from being a dwarf if your character already has Martial weapon proficiency?
It's not like species exists in a vacuum. The mixture between species, class and background lets you create a mixed heritage character that's covering all (or at least most) of the bases.