i got the same problem here. Installed the mod with six updater.
Someone said earlier that we had to get old files? but wich ones? People are being really too unclear about things here.
EDIT: So i apparently found a fix: if you run the ACE mod with the stalker addon it fixes the stalker models.
But in the bloodsucker hunt mission, there is no mutants and the bloodsucker you have to kill doesnt attack you
http://puu.sh/3VcU1.jpg (277 kB)
running the game with six updater again