It reminds me, possibly a little, of the game Predator: Concrete Jungle.
Just a little.
You might want to zero in on the time it's set in, too - Mid 80's or Modern Time, there's about 30 years difference there: It might work out with having the first part of the story (BoogeyPredator) in the 80's, then the next part in modern times - a chance to play with both old and new tech: also, the possibility of having a young gang-banger having his head stoved in by one of those archaic cell phones the shape and size of a brick.
As far as concepts go - the only thing I'm working on at the moment fan-fiction wise is the Aliens: Blood that I've been posting. Which reminds me, I may post another couple up there. I've been reviewing much of my older material from when I lived and breathed Aliens/ Predator, most of it 15 years old, and much of it is terrible. Morphing Aliens, a Predator taking a 10 year old girl under a protective wing, a race of mutant that farm aliens and use them like livestock... no no no.