imperialscum said:
his disappearence
Like showing a flashback of him disappearing?
reasons for his disappearence
I’m not sure if you were paying attention or not but Han told Rey and Finn he left because he felt guilty about Kylo turning and killing all of his students…
See KOTOR for how something like that is done properly.
The Revan reveal was a plot twist so you can’t write a story around something you already know in a manner in which you would write a reveal. That wouldn’t make one iota of sense.