Replace Class Abilities

Hello everyone, I play a "evil campaign" with some friends of mine, and I was interested in making the Oathbreaker even more evil.

The idea was to change his Lay on Hands anda Aura of Protection to something else, but I don't know how to do it or if it is even possible. 

Any information is welcomed!

It's not possible, you could add a subclass feature that adds additional effect options to it but you cannot remove or alter class features.

Anything can be changed.

Aura of Protection could become Aura of Vulnerability, giving a saving throw penalty to all creatures within range.

An evil version of lay on hands, could be used to harm instead of heal.  OR, it could be used to heal undead.

Go with your heart.