As it is, it would fit very well as a Cthulhu monograph. I'm not sure I would recommend it though, as its then likely to stop there. (Cthulhu Rising f.ex. have tons of stuff on their website, but only one little monograph published). You're probably better off with GORE.
I would very much like to see it for BRP, but I think the horror part might be too might similar to Cthulhu for them to pick up on it. It's worth a try though. If the cthulhu-like mythos would be switched with "real-world based" mythos, as you suggested earlier, the setting would be a real kicker and perfect for BRP. Then they'd be crazy not to pick it up!
Good luck!
SGL.