Indeed, I doubt there were very many scripts for a fourth season. The few that did exist probably ended up becoming TAS episodes or Phase II scripts, which themselves were converted into TNG episodes.
There was D.C. Fontana's story about Joanna, McCoy's daughter -- "The Stars of Sargasso". I think she got pretty far into that one. (Of course, she had a head start, having originally written Joanna into a story called "Joanna" that evolved instead into "The Way to Eden".)