Re: Hero System for Horror gaming
I always do this, even with Hero. I'm the polar opposite of those guys who need game stats for flashlights - very rarely will I actually do a full writeup of a monster or even an NPC. If I want X effect, I write up X effect with little regard for what Powers/Advantages/et al. are required. That stuff is for point balance and as GM, I'm not beholden to balance. When I run horror the game effects serve the mood, not themselves.
That said, Hero has enough general mechanisms to use as guidelines that I don't run into mid-game mechanical conflicts. If I can resolve Champions power interactions on the fly, power interactions in horror are a piece of cake.
Absolutely. I mainly invent critters unique to the given scenario. When I do use an established monster, I generally make my own version (unless the book version happens to be a good match for what I had in mind).