Here's what I'd do:
- Hire Kevin Smith and/or Frank Miller to write it (or myself =D).
- MSJ's version of the character hinted towards having increased strength. I'd retcon his origin to make it 100% clear that the liquid that entered his body gave him slight super-strength, speed, and stamina (not on level with Spider-Man, but strong enough to kick over a car or leap between buildings the way he does in the comics/film constantly) in an attempt to explain some of his feats in the films and comics.
- Cast the best actor for Daredevil regardless of whether or not he's a star.
- Bring back most of the supporting actors (Colin Farrell, Jon Favreau, etc)
- Give it an R rating (my budget would be low enough as to guarantee a profit even with an R rating).
- Use dark lighting in tandem with a bit of the bleach bypass technique resulting in a movie that is visually similar to a cross between Batman and Payback.
- No camp or scenes geared towards kids. This includes cross-gender battles in playgrounds over a name and phone number.
- I'd emphasize the duality of the Daredevil character more, instead of letting him become a poor man's Batman. He's a lawyer who's a vigilante, and a devout Catholic who beats the **** out of sinners. He should be constantly torn between what the law says and what it ends up doing and between what he believes he must do for his father and what he believes he must do for The Father.
- Much less CGI.
- More realistic fight scenes (no spinning on ceiling fans or scaling gigantic organs like he's New York's other roof-hopping vigilante).
Just a few ideas.