I would not build a class/char with a special item or potion in mind. The stupidly designed headband from Gump was luckily changed from 18 to 17 Int, this could happen to similarly weird designs too, hopefully, for example being able to get a 21 Str potion in an amount that nullyfies any class based properties.
Did you read about the Eldritch Knight a bit? We don't know what Larian will make with the higher levels, but maybe it is at least generally after the DnD rules, so you could use f.e. this:
https://rpgbot.net/dnd5/characters/classes/fighter/subclasses/eldritch-knight/With your build I too do not really get what the high Dex is for. Is it for RP? I like Barbarian and Fighter but I cannot imagine my char as especially strong, so currently I'm trying a Dex based Battlemaster Fighter, to use ranged mainly. But for an Eldritch Knight high Dex does not seem that important as ranged weapons might not be the best choice.
I don't like heavy armor from the idea and looks, so the +2 for medium armor from high Dex is nice for me. But normally with as Fighter I would use heavy armor (although heavy armor in DnD is really crab, the best is a whopping 1 AC more than best medium + Dex modifier, fantastic ...; beware, in DnD at least most heavy armor has a Str requirement, the chain mail currently in BG3 however has not) and put Dex lower. 16 Str-10 Dex-16 Con-14 Int-... maybe, if not at start (not possible with an elf, I think) then at lvl 4.
