More defensive flexibility.
When the defensive replacements come in, I'd like the ability to put in a new CF, slide my existing CF over to LF, and take my LF out of the game.
Also, say I have a OF who I start at all 3 OF positions, or a Util IF. His defensive recs might be slightly below average for a SS, but very good for a 2B. I'd like to make it so if I start him at SS he's eligible to be taken out for defense, but if I start him at 2B he'll remain in the game.
Another one: when looking at the league leaders page, make it so when you mouse over an abbreviation for a statstic, a window pops up telling you what the stat is and how it's computed. For example, mouse over on "AVG" and a window shows "Batting Average. AVG="Hits/AB""