True, they would have problems with age, but that's one of those suspensions of disbeliefs that I'd be okay with. I'd be okay with it, because the quality of the stories are so great. The crux of my point was that they should apply EU plots to the new generation. This wouldn't be difficult to do.
Example story synthesis: Have Thrawn appear in the galaxy in TFA, and have him rally the Imperial Remnant/First Order. He's charismatic, so he rallies systems still feeling loyal to the Empire. This would allow the filmmakers to explore pro-Empire points of view, something new to SW films. As for his age, just have Chiss live a long time. As to where he was, he was in the Unknown Regions trying to find and destroy the Yuuzhan Vong, but the fleet and frontier bases he was given were all destroyed. As to his motivation, have Thrawn be like Thanos; Thrawn has the burden of knowledge about what's coming. For added fun, mix in some Shadows story points: Instead of Xizor hunting Luke, have him hunt Rey. Have Xizor wanting to appease Thrawn or Snoke, instead of Palpatine.
Structurally, the Heir to the Empire-arc comprises the first three movies. The next trilogy deals with the galaxy fighting the Yuuzhan Vong. In the Yuuzhan Vong trilogy, have Rey learn the Dark Side like Luke does in Dark Empire, because she's desperate to stop the menace. That would add interesting character development. Then have the Yuuzhan Vong leader be Darth Revan, because why the hell not? If Disney would just mix and match stories, they could make some amazing films.
In regards to Dark Empire, I'd argue that it's much different than TLJ. For example, I didn't like the Luke-Kylo tent scene at all, but I really liked DE. Upon reflection, I think this is because DE was a character's slow descent, via misjudgment and desperation, into a darkness that almost overcame him. In short, Luke had gradual, believable, character development: "I found knowledge there... All the dark things father knew so well... The ability to control others... To destroy others, if I so choose. Ben warned me... Yoda warned me... "Once you start down that dark path, forever will it dominate your destiny..." But I had to do it Leia. I had to know my father... I had to know why he chose the Dark Side."
To me, that's much better motivation than: "Jedi make mistakes. Mistakes am bad. Jedi must die now. Kylo think bad thoughts. Bad thoughts am bad. Him must die now. Oh wait, me change mind because me read movie's script." If they had built it up more, it wouldn't have been the character development whiplash that it was.
