I've currently read your comments and really appreciate your input. I am however afraid not all of these mechanics work will in Agent no 6 but I do like a game in the style of House of the Dead 1996, as you descriped. Maybe I can put some things together though!
As I am a solo developer, and full-time student, this can be really tough to tackle (at least in short notice). Furthermore, I will be focussing on at least one other project before fully starting on this.