For season 2, I personally think they'd definitely do best to tell totally new stories with some of the girls they didn't do last time. There are a whole bunch more from some of the other games who haven't appeared yet, or haven't had their own arcs. Someone posted a pic showing loads of them a few pages back IIRC.
Since everyone has their own favourite characters, picking just a few from the original series, or sticking with just one of them, would be guaranteed to piss of at least some fans. Go with new characters, and they avoid having people go "why did they choose Sae!? She's boring, I'm not watching this!"
In my opinion, the first season ruined most of the girls and had terrible flow. They gave little reason for the girls to suddenly fall for the main character in episode 3 and downright ruined certain characters with the cheesy dialogue and fanservice. It was embarrassing to watch just because how much they were catering to the avg shy guy who could never get a date in high school. Sorry but relationships don't work like that, girls don't magically fall in love with you just because you listen to their troubles or lick their knees. Those people are usually 'friendzoned'.
I pretty much agree with this. The first series was far too corny and idealistic (for want of a better word). That was kind of what gave it it's charm, but it was really annoying. I actually quite liked the omnibus format, but it would probably have been improved if they dropped one or two of the characters and gave the rest more screentime.
I wonder if any of the games have English translations? I'm curious to know if they had the same issues, or if it was just the anime.