[Charlie Hough]

Yes, historical rookies can be put into the free agent pool. The game can do this automatically. Just keep in mind that the AI has no means of evaluating the long-term future value of these players beyond their initial potential ratings. So it's incredibly easy for the human GM to dominate and sign a lot of top historical rookies or get the better of the AI in trades.

As far as feeder leagues go, I don't think you can assign players to them. Feeder leagues are really for producing players that feed into your draft or minors. You should use minors instead and either choose to have the game use ghost players to fill out the minor league rosters or use the option to block fictional players from the majors. I'd use ghost players, otherwise the AI will treat fictional players like they have value, even though they can never play in the majors.