There's several minor characters I wish they kept around. Ensign Gomez was another great character with a lot of potential for growth. I mean, she was a little obnoxious, but the idea of having a brilliant, attractive, yet naive and semi-neurotic female character evolving into something more and proving herself was a great idea. They eventually fulfilled that with Barclay, but Gomez would have been wonderful, and a possible love interest for Geordi.
Selar was nice, if they even remotely fleshed out her character. Even Gomez had more characterization than Selar.