I was thinking of something similar for my long planned BPRD game. Special Agents of the Bureau of Paranormal Research and Defence Vs. various monsters....
Oh yes, BPRD! Now we're talking.
I had seen what Matakishi had done with Crossfire, I think it was Crossfire, making it into Hellfire. I like the looks of it, but I'm not a huge fan of Crossfire.
I was thinking to play around with
I Aint Been Shot Mum, try and see if the card activation could really bring the Mythos elements out. Add some additional powers to the Big Men as well supernatural event cards. The Mythos creatures could almost take the place of vehicles, with a certain number of strike dice. Ok, I'm kinda liking this already. I think adding some kind of Terror / Fear causing element to the Mythos creatures would be essential though, so that would require a few playtests to get right.
To my shame, I have yet to play Pulp Alley, I really need to get on that.