If you did play as a Paladin which in-game cause would you choose?
You can’t pick none as that defies the definition of paladin.
You have a few things to choose from.
Skatsim
Cathedral of Light
Zakarum
Knights of Westmarch
The Triune or Khazra, if you want to go Dark Knight.
Stamping out dupes with the light of purity aura!
Light of Purity Aura - Destroy all sinful items within this aura. Any owner of destroyed items is stunned for 777,777 seconds and cant use skills.
To hell with the Paladins bring on the Order of Kormac the Templars Reborn. 
What do you call a templar that just keeps coming back from the dead?
Permalar! Not so temp anymore am I!!! 
Im here all week! Tip your forum goers. 
Can I take up Lilith’s banner instead? I mean her blood is coursing through my veins.
Of course thinking about it now, the lore canon in this Diablo game is us drinking Lilith’s blood and being infected so to speak. I don’t see a Paladin of any kind doing this. They wouldn’t purposely taint themselves, it would go against everything they stood for.
Now that Tyrael is mortal and flesh and blood ask him for a blood transfusion.
Spiritborn are clean. Maybe some of them would like to try out the colder weather of Scosglen and take up a shield.
I hope they will make a versatile class with paladin, not just a copy paste from past version.
Path A - shield flail holy midranged like d3 crusader
Path B - 2h weapon with shadow dmg like last epoch void knight
Path C - staff wand scepter based holy caster, something like cleric
The lore will be most likely tied to akarats chir chur return and how they rebuild the order.