We’ve seen a lot of Anakin in the prequels and The Clone Wars series, but not a whole lot of Vader since the Originals. He had a little part in Rogue One and popped up in the animated series, but most of Vader still resides in the Originals, so I don’t feel overwhelmed with Vader.
Before the prequels were released, I envisioned a lot more of Vader hunting down Jedi. Now that we have Anakin’s backstory, I’m not sure a movie with Vader as the central character would fit well. I think instead you would have to make something centered around a group of Jedi who survived Order 66 and are being hunted by Vader. Focus on and build those characters, then let Vader do what he does best, be the menacing villain who inspires fear. That sounds a lot like Rogue One with more Jedi, so maybe that wouldn’t fit well either.
Perhaps Vader best left to surprise cameos that leave us wanting more.