There are enough gun shooting characters it could work, hell, people with ranged powers too or ranged weapons even if they aren't guns so that Hawkeye can be in.
Just saying, you could put:
Punisher
Deadpool
Hawkeye
Nick Fury
Blade
Rocket Racoon
Cable
Bullseye(who can just use random shit)
Crossbones
Silver Sable
War Machine
Iron Man
Doctor Strange(Come on, he can just cast spells)
Human Torch
Iceman(both can just do variations of throwing flames and ice)
Cyclops
Storm
Gambit
Domino
And so forth, characters that aren't gun users can work...it just depends on execution.
Just saying, you could put:
Punisher
Deadpool
Hawkeye
Nick Fury
Blade
Rocket Racoon
Cable
Bullseye(who can just use random shit)
Crossbones
Silver Sable
War Machine
Iron Man
Doctor Strange(Come on, he can just cast spells)
Human Torch
Iceman(both can just do variations of throwing flames and ice)
Cyclops
Storm
Gambit
Domino
And so forth, characters that aren't gun users can work...it just depends on execution.