I know that Tasha Yar isn't high on many lists of fan favourite characters, due to some cringy lines and wooden acting--but then again there was a lot of that in S1--however I always kinda liked her, plus it was good to see a woman heading up Security on the Federation flagship.
What if "Skin of Evil" had gone a little differently and she hadn't been killed off? Denise Crosby would've probably gotten more comfortable in the role, she and the writers would understand the character better and hopefully wouldn't give her any more "don't do drugs" speeches, whilst also building on bits and pieces they liked (I remember Crosby saying that she liked the little moment between her and Worf at the start of the episode, and if they'd written more scenes like that she would've stayed) as well as developing relationships among the characters.
It would also have kept a female character in a strong post on the Bridge, as well as on away teams and delving into her own traumatic past, all of which would have worked out pretty well for her.
This of course leads to uproars from the Worf fans about how he'd be neglected and left to waste away doing nothing. However, as they went into S2 Geordi was moved from the conn to Engineering which gave him far more to do. Worf would then have been the logical choice to sit next to Data, leaving Wesley to sit at a science console whenever he was permitted onto the Bridge (which is another 'win' as he wouldn't be right in your face).
Looking back at Worf's character post-SoE, most of the stories that focus on him are to do with his being Klingon rather than Security Chief, all of which could have been done with Yar still on the ship. There was also an instance in S1 when Yar wanted more muscle on a mission and so asked for Worf to join them, which again could have been continued throughout the rest of TNG when needed.