Thrawn does show up in The Clone Wars animated series, fighting alongside Anakin Skywalker and showing great admiration for him. But there’s not much shown about Thrawn’s personal travels across the Galaxy and his relationship to Darth Vader later on.
The Thrawn Trilogy, a series of novels written by Timothy Zahn, narrates the rise of Imperial Grand General Thrawn, a warlord for the Emperor who returns from the outer reaches of the galaxy after being given the news of Vader’s death to rebuild the Empire. And he doesn’t do too bad, throwing together a massive army from what’s left of Imperials, along with Jedi that has devoted themselves to the Dark Side.
Covering the events between The Return of the Jedi and The Force Awakens, one of the Star Wars stories we want to see on Disney Plus would be an introduction to Thrawn’s character and a show that covers his ambitious rise to Empirical power. It wasn’t all sunshine and roses after Vader’s passing and Palpatine’s retreat into the shadows.
Thrawn made sure of that. But not only is his character a big bad, but he’s also a fascinating strategist and it would certainly be different to have a show starring a villain of the Star Wars galaxy, rather than always spotlighting the heroes.