How about on how expansion, contraction, and relocating teams has changed the league? You could go with more recent history like the Expos, Marlins, Devil Rays, and Rockies...and the annual threat to contract the Twins. Or you could go way back to the Dodgers, Giants, etc. Another idea for a paper could be on free agency in baseball. I don't know if you've ever seen the Ken Burns series on baseball, but it's really interesting to see how much power the "reserve clause" gave owners over players until Curt Flood finally became the sports first free agent in the 70's.