I'm also quite interested in the concept, as I totally love Risk of Rain. (There's a four pack on the humble bundle for extremely cheap if you've got seven dollars. Really great deal.) Will you be allowing us to play as any character, even HAN-D or Acrid? I think playing Acrid would be very interesting seeing as you're a beast and not a man. Would lead to pretty good development in growing closer to the team. As for my personal choice, I might end up playing as the Sniper or maybe the Enforcer perhaps. The Enforcer sounds pretty fun for combat seeing as you have a shield and shotgun. 

I do wonder what the combat system will be like.