I have created two fictional leagues with the same format. They are in a sense "competing" leagues for me. I try to think of backstories that will link the leagues, and now with Pierre's editor I can switch players between leagues.
Edit names and create player profiles. That is what I did and it worked out great.
Here are some PP's if you are interested in an example.
www.nlbaseball.net/news/march/6.htm - Robbie Schaub
www.nlbaseball.net/news/march/5.htm - Clay Schwartz
www.nlbaseball.net/news/march/4.htm - Dmitri Viskolov
www.nlbaseball.net/news/march/3.htm - Vevet Jones
www.nlbaseball.net/news/march/2.htm - Jason Cisco
www.nlbaseball.net/FLB/April/2.htm - Tuffy Rhodes
www.nlbaseball.net/FLB/April/3.htm - John Rocker