I played around with Promotion and Relegation in 2006. Generally it worked well. I imported 2005 from Lahman and split up MLB into 3 separate leagues based on record. As far as minor league systems, I didn't have to move those actually. For example the game allowed the same AAA league have affiliates for multiple major leagues. I think I just got tired of how long it took to test out different settings. One of the issues I struggled with was how to correctly model the financial advantage of being in the top tier versus the third tier. Also each league had it's own draft and I decided I wanted the top tier to get the best talent so the league PCMs had to be adjusted accordingly.
One note: In OOTP 2006 the act of relegation had to be done after the history for the previous year was finalized. If I remember correctly for a standard league this was sometime in February.
