I saw such a plugin it's named csx extended made by souvikdas95, it has that option.
I experienced a really bad moment when I tried to block death count for zombies on basebuilder server because players weren't attacking humans to not loose rank. And I was needed to recompile source code of the csx module.
But it's OK, I don't think someone else would experience such a necessity to block deaths count or to change frags number.