I would do like the old cRPG's did and have "normal" (advantage is given out like candy, everyone can bonus disengage) and "5e core rules" (advantage has strict requirements, only rogues can bonus disengage) difficulty settings. I don't particularly like 5e rules, but they are extremely balanced to the point than +1 or -1 here or there can break everything from the over-tuning let alone adding new sources of advantage.
Yes, height advantage makes sense and that's why 2e had a bonus for high ground that everyone tried to get. In 5e, all of that is already assumed that you are getting the best possible position to your skills and the enemy is doing the same. If you add advantage for the realism there, you are double dipping the benefits without adding other downsides to the fight, because it is baked into the rule system in other ways.
I think cRPG's are incredibly well suited for the older rule sets where you meticulously added +2 for this and -1 for that and it made combat take a long time at a table, but can be instant for the game to compute. Sadly, this is a 5e based game, and as such, shouldn't change balancing mechanics when it isn't necessary to translate to the cRPG medium. Because afaik they are not allowed by Wizards to significantly deviate from the 5e rules, and these minor tweaks can be disasterous for balance if you don't go all in with customizing the rules.
You can't have it both ways; you can't have the dumbed down ruleset and add the "realism" of "considering the details of the situation" to a system designed to account for all of that with hand waves. The problem is most computer gamers want detailed, nuanced systems since cRPG's allow for near infinite complexity to be happening behind the scene and that isn't 5e's mindset at all.
5e is great for keeping a fast pace at a table of six people all doing mental math. That said, I view the decision to use it in a cRPG as "well, that's the devil's bargain Larian had to make to get the license from Wizard's to make BG3." So I'll give them a lot of slack for having to try to make that system seem like it has any depth in a cRPG and focus on the story being told. I think BG3 could have been pretty slick if Larian had been free to use their own "interpretation" of the D&D ruleset. But, since they can't, I do think they should just accept that they can't try to squeeze in extra advantage here and there where it makes total sense from fun, gameplay, and realism etc, but breaks this brittle, fragile... I mean streamlined, quick paced, and highly balanced rule system from Wizards of the Coast TM.