Any character should have the choice to have a god or not. WoTC has been moving away from alignments.
Good old LG paladin is long gone.
Player choice and agency is the way.
But making it clear when a pally will break their path would be great. I did a test, if I killed some enemies oath broken. Knock them out then my party kills them- oath not broken.
You should have that choice for sure, however your choice should not be grounds for rewriting entire classes and their lore and the way they work.
I don't mind if some people want to play an atheist cleric or paladin, that's actually fine, but that shouldn't fundamentally affect the way the class as a concept.
A paladin that is an atheist could for example, still be devoted to Justice, and he would still be granted divine powers through the divine portfolio of Justice with the approval of the God of Justice, Tyr. The difference between an atheist and a believer Paladin in this case would just come down to having to deal with Kelemvor in the afterlife.
However, the powers of an atheist Paladin would still be granted by divine forces and it wouldn't be an internal power within the atheist Paladin. If you want internal power that comes through the force of personality, the self, that's pretty much what a sorcerer is, which is a perfectly fine class btw, but it's not what a paladin is.
