[NoOne]

20 rounds is plenty for a single minor league per level affiliate per mlb team and no "Rules" for you MiL relating to max age or max service time. (if that makes sense) -- no duplicate A's or rookies for anyone etc.

with no rules, it'll take at least 12 years to turnover an mil system. 2-to-3years per level. so you need about 1/2 to 1/3rd of a team from each draft year and you never run low on players.

if just one team has 2 rookie teams, you need quite a few more draft rounds each year or that 1 team will constantly run out of players in their mil system. *must be based on largest mil system - redundant teams at same level, but not so much # of tiers.

you want more than the minimum so that the best players can float through system as developement dictates without causing a lack of players at some level. so, maybe minimum to fill their teams plus ~5-10 more per year.

i'd even suggest making ~5 extra rounds of players beyond # of rounds in draft for a healthy mil FA pool. (above and beyond the extra "~5-10" suggestion)

once you get that worked out, then do the above math in previous posts for # of hs/college teams required for "that" many rounds of players created * # of teams.