Star Trek: Saavik. Recast with someone closer to the feisty Kirstie Alley version, as opposed to the more subdued replacement, and set during the movie time frame. The Saavik of Star Trek II was one of the most interesting characters Star Trek produced and they dropped the ball almost instantly.
Star Trek: Ro Laren. Michelle Forbes could still do this, set concurrently with the Picard series. They didn't make the most of her as a semiregular on TNG, but "Preemptive Strike" was the best episode of the show's last season. Yes, I'll take it over "All Good Things."