I hear ya... I think every group has at least one player that loves making the most powerful thing they can concoct, storyline be damned. I know I have one in my group, but he doesn't game with us too often...
I have convinced my players at a story-driven game is simply more interesting than a comparison of numbers and how many dice you can throw and our games have become so much more enjoyable.
As for "weak" characters, we consider it "room to grow". The Christian soldier character (either called Apostle or Templar...whenever the player decides) spent almost all of his Knowledge Points on things he may never use in the shadows (Christian History [The Crusades], Bible verses, Latin), is renaming his adept powers to titles reflecting his faith (Killing Hands = Touch of God, Increased Reflexes = Lord's Grace) and lots of other flavourful stuff. But when he picked skills, all his skills are at 3 and 2. Some may consider it weak, but the concept behind the character is someone fairly new to the shadows, who hasn't undergone extensive training yet. He has just decided that it was God's will to purge the city's underside of heathens...
As I mentioned before, not sure how effective he'll be, but we're certainly having fun developing the character... and having fun is what we're here for, right?

SR13