The recent Adventurers League Players Guide has already adopted the official ruling that will appear in the upcoming Tashas Cauldron of Everything.
Essentially, when your race (heritage) or subrace (culture) gains an ability score improvement, you can instead put it on any ability you want. So if your high elf is Dexterity +2 and Intelligence +1, you can instead make it Charisma +2 and Intelligence +1. Or Strength +2 and Constitution +1. Any ability you want, depending on your character concept.
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If you’d like your character to follow their own path, you may ignore your Ability Score Increase trait and assign ability score increases tailored to your character. Here’s how to do it: take any ability score increase you gain in your race or subrace and apply it to an ability score of your choice. If you gain more than one increase, you can’t apply those increases to the same ability score, and you can’t increase a score above 20.
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With this official rule now the reality, Level Up might as well decouple the ability improvements from Background. Or rather, allow the Backgrounds to "recommend" a certain ability, but let the player put the ability improvement wherever one wants.
Essentially, when your race (heritage) or subrace (culture) gains an ability score improvement, you can instead put it on any ability you want. So if your high elf is Dexterity +2 and Intelligence +1, you can instead make it Charisma +2 and Intelligence +1. Or Strength +2 and Constitution +1. Any ability you want, depending on your character concept.
"
If you’d like your character to follow their own path, you may ignore your Ability Score Increase trait and assign ability score increases tailored to your character. Here’s how to do it: take any ability score increase you gain in your race or subrace and apply it to an ability score of your choice. If you gain more than one increase, you can’t apply those increases to the same ability score, and you can’t increase a score above 20.
"
With this official rule now the reality, Level Up might as well decouple the ability improvements from Background. Or rather, allow the Backgrounds to "recommend" a certain ability, but let the player put the ability improvement wherever one wants.