I'm totally looking forward to this project. Now, to fuel some hype, I'll speculate.
It seems the coins are for buying power-ups. From what I can tell, when he froze time, the pick-up message indicated that he had bought something. Thus, the HUD's interface is most likely for buying said power-ups. Also, from the two weapons we've seen (no counting the one he never fired, the assault rifle looking-thing), we can assume that they are very Devil May Cry inspired (The shotgun uses sounds from DMC, along with the Pistols, and they each kind of match the designs of weapons from DMC)
I can't wait to see this in action someday!