Could not agree with you guys more. A minor league (or farm system) roster is a must have. A MUST! Every other fantasy sports provider has this feature, but I stick with Yahoo because I have several leagues that have been on Yahoo for years and I'm use to / prefer Yahoo's user interface. Come on Yahoo let's see some urgency in making your leagues more friendly to keeper and dynasty leagues!

Another interesting feature would be to mark players as minor league players by whatever stat you want to use. For instance, in the settings area I can say the minor league eligibility requirement for hitters to remain a minor leaguer is 130 career ABs in the majors. Every player who doesnt meet this shows up as a minor leaguer and you should be able to sort by this in the player list drop down menu (show only minor leaguer players). Same for pitchers (like 50 career IP). When a player reaches that threshold the minor league tag goes away. You would then be able to have a draft for only players categorized as "minor leaguers" and only players with "minor league" eligibility could be added to a farm system or minor league roster.

Just some ideas that really shouldn't be very hard to implement if you have some decent programmers there. :p