You cannot calculate the Modifiers more accurately than how
OOTP does it for maor league historical simulations, AND you cannot use some pre-made modifier settings to get what you want. Simulations are dynamic and that's why
OOTP actually calculates the modifier values each season.
I would suggest not using minor leagues ina hitorical simulation. All the players that come into historical are major league players and they debut in their first major league season. There's simply not enough players to run an entire minor league system...and using major leageurs to fill the minor leageus makes little sense anyway.