The good news is the expanded material still does justice to the ending of Return of the Jedi, regardless of whether Vader is redeemed.
It still doesn’t explain why Obi-Wan and Yoda were cool with him being around in the Force ghost afterlife, but perhaps stuff like that gets brushed aside in death.
After all, Anakin aligned with the Emperor to effectively protect his family, so it makes sense that protecting Luke would ultimately overrule the allegiance he has to Palpatine.