I didn't actually play Paladin, but seen enough from others.
I will say that Oathbreaker should either be chosen at creation for lore purposes. Someone intending to be an Oathbreaker has to pick something else and intentionally mess things up at the beginning of the game, which may also affect party members.
OR
Oathbreaker options should have tags in dialogue leading you GRADUALLY to this transition but letting it be known this is going down an Oathbreaker path.
Larian swung for the fences trying to do too much and missed...as usual...
A lot of their shortcomings really come because they can't just keep it simple and do what is required only.
Going Oathbreaker is 100% optional. There is nothing that stop you role-playing a slow descent to "evil" in the EA. The tools are there. The Oathbreaker is filling in the role for the confessional that a GM controlled cleric/paladin of the same order would fill in a table-top session to keep your oath. The game doesn't force you to pick Oathbreaker after breaking your oath, it's a choice done via dialogue. You can also choose to atone and it comes with a cutscene where you say your oath(again).
People act as if breaking your oath is the end of the world, it's not, the PHB suggest ways to cause Paladin to oath break by accident. Managing your oaths is part of playing the class like learning spells are for Wizard. It's supposed to happen and your supposed to feel repentant about it unless you want to change (sub)class.
