I've submitted the same suggestions for at least 3 years now and (not surprisingly) Yahoo has not acted on them.

1.  Put a filter in the Player Search screen for either AB or IP.  It's incredibly annoying to try and search for players who have the best ratio stats (AVG, OPS, ERA, WHIP, etc.) over a certain period of time (season to date, last 7 days, last 30 days, etc.) when there is NO AB or IP filter.  The first pitcher listed will be some RP that has thrown 1 IP on the year with an ERA of 0.00 and the same with hitters and AVG or OPS.  These filters should be included so I can search for batters with the highest average or K/BB ratio over the past 30 days and actually get players that played on a regular basis---not someone who had 1 AB and got a hit in that 1 AB.

2.  There need to be weekly leagues that allow daily transactions.  RIght now the 2 options are daily  (roster moves everday) & weekly (no rosters moves at all including inside your lineup).  A much better option would be a hybrid of the two (which I currently use in my oldest league), especially for H2H leagues.  You could add/drop players only for the following week but you can make lineup changes on a daily basis.  In other words, you can't add a bunch of pitchers to stream during your H2H matchup but if someone on your team gets injured, you can replace them with another bench player.  This option would solve the problems of each format (daily--can constantly stream pitchers and/or add hitters for off days, weekly--players get hurt and you lose that roster spot for the rest of the week).