Zerrubabel, To me chosen oath and oath to a deity are connected. But I was actually referring to Oath of Devotion, ancients etc.
My point was if a paladin who worships a deity breaks that Oath, its probably that deity who tales those powers away. It Gets clunky when I try and explain it cos for my Paladins (player or dm) they actually swear 2/3 oaths. One of conviction/principle/goal (ancients etc) one to their god, and a general one to strive to uphold The Paladin virtues (scag).
Anyway back to BG3. Ive been playing past 2 days with a mod that basically copies Cleric deity list in character creation. Dialogue options are same as Cleric except it says Paladin «insert deity here». Just Even that implemented would be ok honestly. Would require near zero extra work as well. Heck a midder did it perfectly and file sine is miniscule. Its just copy paste from one class to another. Problem fixed (sort of).
They do need to explain The oaths more clearly in game though (what you can and cannot do). Right now you become an oathbreaker for attacking and killing a goblin torturer.
Then the solution is to borrow the Cleric's tags and have the following options:
"Paladin of X" Choose a deity, the characteristics of that oath makes you sponsored by that deity (not all deities are available for all oaths), and if you break the oath you break your connection to the deity. I'm not sure if you have to be "sworn" to the deity though. I think you are sworn to the terms of the oath, and the deity grants you power. More like a Divine Warlock than a cleric. You abide by the terms of the contract, not the whims of the deity.
"None," You follow your oath and your oath alone. Through this, you draw on the Divine Magic through many Divine Realms which overlap with the nature of your oath. Should you break your oath, this tenuous connection to the many realms would be shattered. (No Paladin of X tag included).