I, too, think Sela was just a bad idea. Even a brainwashed AU Tasha as Sela would be an improvement as far as I'm concerned, but avoiding her altogether would be better.
I think Worf would have probably stayed a more secondary character, with the occasional "very special" Klingon episodes staying more intact. I, personally, would have liked to have seen him go to DS9 in season six and become a full-fledged main character.
Alternately, what if Yar went to DS9? What if Yar became the captain of Voyager?