“Perhaps if the MC is in a wheel chair or agoraphobic his obstacle would make his story more interesting/original, or what if the killer had a unique method of berrying people alive so the MC has only a few days to find the victims before they suffocate.”
The fact that he’s not a cop is what is the challenge. He doesn’t have training, weapons, or resources to take on a seasoned killer. Giving him a disability would make the story less believable, because of his lack of training and disability combined. .
It seems to differ in that it’s not a mystery at all; he knows who did it and is trying to stop him. He may have to figure out where he’s going and such, but as the genre is labelled ‘Horror’ it seems more horror than police procedural.
Besides, it is similar to an established idea, the police procedural, yet it is different. While maybe you have run dry on standard police types(I don’t even watch procedural so I know how you feel), studios are still looking for them. It different enough to be a bit unique but familiar enough to probably not be considered a risk.
I think making the killer unique is probably the way to go.?