Oh, you are right, direct trading is a bad idea. Anyway I see this suggestion only like that it would be done by representing of all putted players to a TL somewhere to the undermenu into a league page. And they would be on the TL anyway.
That means everytime you will put the player into TL, he will be shown on that submenu on your league.
Only issue I see on that is that your opponents would have good knowledge about your players which were putted on the TL, because this would help them, however Big Brother is watching you anyway through your roster page, while it takes slightly more work.
So only issue is the presentation on that submenu, while it is not so big deal in my opinion, because only active users are watching league page every 3 days. Anyway it is for a discussion.
This is not a direct trading, this is a representing. Is my silly habit to use only few percent from the original idea.