You know, hearing about the Vader comics and developing Vader's struggle prior to ROTJ, I'm gonna be honest: I think this sort of development for Vader, while it may seem like a no brainer to do (build upon elements to fuel Vader turning on Palpatine), doesn't work for Vader and Luke's story.
The climax of ROTJ is Luke's unwavering faith in his feelings and familial bond in Vader sparking a sense of humanity that Vader had long since thought was dead. Vader spends the movie telling Luke, in a perfect display of the dark side's hold, that he's given up, that he serves Palpatine not out of loyalty or profit, but because he see's no other path. Anakin Skywalker is dead, all that's left is an instrument of destruction who lost all his humanity. He turns to the light because watching his son getting tortured while still pleading for his help makes him realise that his humanity is still there, even if faint, proving that Anakin Skywalker is alive and he wants to help his son.
All of these elements become far weaker when you change it from 'Luke creates cracks in Vader's armour, both figuratively and literally, exposing Anakin for the first time in years' to 'Luke manages to get through to Anakin after years of other people already making Vader question himself and face his still beating humanity multiple times'. Makes Luke's victory feel more like he just so happened to be the hundredth customer rather than him having a admirable strength of will and hope.