I"m definitely interested in this. It hits quite a few of my buttons.
However, we really need a character sheet of some sort. We're also going to need a somewhat specific setting, so that we know where we're starting and what we're starting with.
I would also like to know how far into this story we're starting. I'm of the opinion that if we start with the Alpha, this thread will die a quick fiery death. That could be avoided with a very good hand controlling the plot line. However, I think the best chance of survival for this would be starting a few years into the invasion. After the effects of the invasion are already settled in. Then we would have a variation on villains, as well as a wide range of potential characters. We would also have more long-term goals.
As I've thought through this post my mind has been reeling as to the possibilities for the first appearance of the Alpha. However, it would still be a very ambitious plot-line to keep everyone going.
My thoughts on guro/snuff. I won't quit over it, but I'd really prefer if any sexually gratifying death and gore scenes were hidden in spoiler tags. However, standard horror stuff that fits into the plot line and isn't sexual sounds par for the course.
Sorry for the long post and requests when I'm just jumping in, but I have high hopes for this, and I really want it to get going well.