As for casting i'm not sure how I feel about Wesley coming back. He's kinda old, and i've read so much about his attitude on set. It makes me bitter and takes me out of the movie. But maybe he's more humble now that his career is over.
If it wasn't for Snipes and Norrington Blade wouldn't be what he is today. Goyer gets way too much credit for his writing but it was Snipes who gives Blade his Bladeness(Coolness). A lot of times Snipes would cut out lines that he thought were not part of Blade's personality. Like he was supposed to cry in the first movie.
Snipes contributions gets overlooked as well to the movies especially in the first 2. He helped design some of the cool weapons in the flicks like Sword boobietrap and the Blade Boomerang in part 2. Also it was Snipes bringing in his Martials Arts team to make the fights in the movies notch ahead of other actions movies that were out at the time. Snipes put a lot of passion into the first 2 films all you have to listen to the commentarys. He even got hurt making the movies and can no longer do the things he used to do martial arts wise.
As of right now Snipes might be too out of shape to play Blade last time I saw him he was looking kind of chunky at the Mayweather vs De La Hoya fight. So I don't think they need a restart. Maybe do an animated version but rated R for HBO, Adult Swim, and give Snipes the option to do the voicing of the character.