I have a solo league doing just that. Medieval League Baseball started in 1346 with 24 teams conducting their initial draft. Both the Catholic League and the Infidel League have three four-team divisions. The Damascus Swords of the Infidel League won the World Championship each of the first three years, but finally lost to the Catholic League's Florence Bankers in the 1349 championship.
After being fired from Florence after three years, I jumped leagues and now manage the Shiraz Vintners. Last year, I was fortunate enough to have my #1 starting pitcher win the Ballista Award and my right fielder win the Charles "The Hammer" Martel award. This year, we'll see if we can take Damascus.
The Penguin Atlas of Medieval History by Colin McEvedy has a good collection of maps from different years (including 1346, which is why I started then). He has population sizes for a large number of cities across Europe. While I did not use the different sizes to set the teams' markets, it was handy for selecting the 24 main cities of the time period.
Potemkin