I think that there should be gun attachments. Heres my ideas.

HOLOGRAPHIC SIGHT= +2 Accuracy

GRIP= Increased mobility while shooting

BULLET UPGRADE= +2 Damage (only counts for guns with only 7/8 damage originally, and bullet upgrade will run out in numbers.)

EXTENDED MAGAZINE= +10 bullets in clip, but less mobility if not using grip also.

UPGRADED MECHANICS= Faster bullet rate

SHORTENED BARREL= Less accuracy (for just spraying)

TACTICAL LASER= A Laser