I meant to give my feedback on these choices.
Ant/Giant Man - Hank Pym
The small town loser, Hank isn't the brightest, but is kind and tries. However life for him hasn't been kind lately. He just lost his job because of a misunderstanding, and his girlfriend broke up with him. That night he drove out just needing fresh air and time to think. It was then he was kidnapped by aliens who abducted him. Hank vanished for over a year, presumed dead and soon forgotten.
When he returns to Earth he suddenly founds himself a super genius with the ability to grow and shrink to extreme sizes. SHIELD brings him in and after helping him get back on his feet and testing him. Give him a new alias and a mission to work at Stark Tech where he's to keep an eye on Tony Stark and what his up too.
I personally believe that Hank Pym is probably the best option of the three you listed. We have plenty of Avengers, so there should be ample opportunities for interaction (particularly in the future when the Avengers form). As long as Janet van Dyne can be MJ's fashion mentor, I'm fine with this idea.
Damien Brooks - Blade
The idea is essentially take the more devil may care style and look of Dante from Devil May Cry and mash him into Blade's fantastical vampire slaying. The same kind of set up, his mother is a brothel lady who got bitten by a vampire while still pregnant with Damien. When Damien was born the vampires killed his mother and raised him to be a ruler of the vampires. However Damien was saved after some years by hunters who helped him understand the truth and train him to become a vampire hunter.
Years later Damien still hunts vampires in the night, his tastes evolving over the decades as he enjoys rock and roll, pizza and wine, and killing vampires.
I don't necessarily see anything wrong with Blade. He just might be isolated at times, since we don't have many Street-Level characters in this game (besides the all-purpose team-up character better known as Spider-Man :D). While that does not mean Blade cannot interact with the other characters (see Nick Fury's Ultimate Avengers. I do believe Blade was on that team), Blade does not have as many "obvious" team-up choices as Hank Pym does.
Vance Astrovik - Justice
The powerful telekinetic superhero who grew up in a horrible home with an abusive father. Vance becomes good friends with Robbie Baldwin, a fellow super powered person. The two decided to become superheroes after high school, but things changed completely when while getting abused by his dad Vance killed his father in accidental self defense.
After pleading guilty Vance quietly served his time and is now a free man, with only Robbie left to be by his side. The two want to travel, be superheroes, and eventually will be starting up the New Warriors.
So which of them do you guys like the most?
I would put Justice as my 2nd choice. Unless Vance is fresh out of high school (i.e. graduated last school year), your idea might hinder any attempts for a Firestar-Justice relationship. Creating the New Warriors would not be a bad idea, although unless other players pick up the other characters, it might be full of NPC's.
Also, I'll try to update the roster as soon as I can get to it.