I also think Ep IX could be salvageable, with a LOT of work put into it by a brilliant filmmaker.
Base it mostly around the Knights of Ren: many flash backs to Kylo and Luke training so that he gets plenty of screentime and we actually see Luke being a badass. Fill in the info on what all went down at the temple, Snoke corrupting Kylo, and how the Knights went their own ways.
Present day story based around the tattered scraps of the rebellion splitting up and finding these lost knights and either convincing them to join the cause against Kylo or defeating them and absorbing their army/influence/resources into the rebellion. This gives Rey a chance to actually be challenged and to have to fight for survival and overcome obstacles/learn lessons, etc.
The endgame sees Rey, Finn, Poe, etc. plus a couple Knights that they swayed to their side vs. Kylo and the full might of the first order armies. Nice climactic battle, roll credits.
Then fucking retire the present day plotline and let Benioff and Weiss reboot the property with a fucking sweet-ass Old Republic series (maybe Darth Bane and the founding of the rule of two), and then some years down the road reboot the current timeline stuff with the Yuuzhan Vong or Darth Krayt, or something... just all new actors please.
None of this will happen though.