Thinking about how before Ansel showed up in The Originals season two, it was hinted that Klaus's birth father was Indigenous.
Of course, this is Klaus/JoMo:
But if Esther can find a spell to make her children immortal, surely she can find one that controls the genetics of a baby in her womb.
What TVD did best wasn't problematic relationships, it was having a character do something horrible and understanding where they were coming from even if you didn't agree with it. I certainly wouldn't want Mikael Mikaelson finding out the truth. (yes, I know, that wouldn't be his last name. I just think it's funny to call him that.)
If Klaus being Klaus derived from not only having his wolf heritage hidden*, but also from the knowledge that the very fabric of his DNA is a lie....yeah, I could understand spending centuries as a madman.
*(it makes sense for the character, but why would you want to be a werewolf?)
Finally, throwing in my idea that a multiverse would fit in with the TVDU. That there would be a version of Klaus that was raised by his father, alongside his tribe and pack. Who possibly had paternal half-siblings. Who crushed on Tatia, who was drawn to the Mikaelson family for reasons he couldn't explain. Who became a big brother figure to Henrik even though Henrik had 3 brothers already. Maybe in this version Henrik never goes and sees the wolves. Maybe he goes alone. Maybe Kol goes with him.
A version of Klaus who was taught by his father how to reign in his anger through art. Who grew up in a warm home. While the Mikaelson family wasn't empty of love, they were certainly harsh. Klaus growing up with someone who understood what he was dealing with. A Klaus who might've had questions about his mother. A version of Klaus that had a different name and face and life.
If being a Petrova doppelganger (mainly Elena and Katherine) is about looking at someone who resembles you down to every freckle and birthmark; searching for some semblance of yourself in the other girl, while simultaneously being horrified of finding it.
Then Klaus and Native!Klaus* meeting each other, how they are supposed to be the same person, but who feel worlds apart. Yes, they both are emotional and like art. That's not unusual. How through time they could fill in the holes in each other’s minds. How each would answer the other’s questions about a life that could’ve been.
*(I feel like I should name this au version of Klaus, but I don't know what it would be).