Cute story! I love baseball and I love Sam/Diane. Also, the only episode I can recall Diane wearing jeans was the season 5 episode: Everyone Imitates Art. I thought she looked absolutely adorable and never understood why the Diane character didn't have a casual look more often. Also, I think Diane can develop her baseball skills more and develop into a capable player. I remember the episode in Season 4 - From Beer to Eternity where we see Diane display somewhat of an "athletic" side, albeit bowling. She was, shockingly, a capable bowler who helped Cheers defeat Gary's Old Town Tavern. So, I think your on point here with your idea of Diane learning baseball.

Love your stories! I laughed out loud, literally! Can tell how close you feel to the characters. Cheers premiered on my 16th birthday. When Shelley left, I swear I cried for two days!
Thanks for the fun!