That said, I do see a future cloud in the sky, in that there's one fundamentally limiting issue that will bite the designers sooner than later.
That is: you want the game to reward build mastery as well as tactical mastery. (D&D always have) And, quite possibly, good roleplaying too. Problem is, with very few exceptions, both kinds of mastery are based on advantage.
And advantage, as you very well know, does not stack. And more to the point, once you start thinking about removing that rule - even for a justified exception - you're opening Pandora's box and you will quickly end up with a full gaggle of stacking rules again.
.......
I foresee a need for WotC to implement something. How that something will look I'm not ready to say. But for discussion's sake, let me suggest an example as a crude and rough illustration.
Say you can get blue advantage from your class features (=build), and red advantage from circumstances (=tactics), and whenever you have purple advantage, "double advantage", you gain a further +2 on your roll with advantage.
(Yes, I'm deliberate with the static bonus, since it means you're much more helped by "double advantage" when advantage would only give you a +1, than when it would give you a +5. Work out the math and you'll see a +2 bonus when you have a 70% chance isn't really a big deal, while a +2 bonus when you must roll a 20, is.
At 70%, advantage means +4 for a total bonus of +4, but with a static +2, advantage only adds another +3 for a total bonus of +5, halving the benefit of the static bonus. At 5%, advantage means +1 for a total of +1, but given a static +2 bonus, advantage now gives +2 for a total of +4
Besides, actually implementing a "double advantage" mechanism as "pick best out of three rolls" would mostly only accomplish a lot of needless die rolling when you really want just say "with double advantage you automatically succeed"...
And automatic success is not where I want to go)