I had that idea actually back when Blood first came out
You got more frags for killing larger and larger groups at once, and extra frags for certain types of kills.
Ive always liked the idea of Blood having Innocents and Blood2 having Civilians. Blood taking place in the past, caught up in the sudden uprising of a cult in a region of the world that exudes evil... In Blood2 they are the patrons of Cabalco, the purchasers of their products. Their own money and materialism paving the way for their subjugation and slaughter. They left no room for innocence in their eagerness to obtain property, no matter how useless it may have been. I dont think Monolith put that much thought into it, but it kinda acts as an ontological origin for the Innocents fleeing for the most part, and the Civilians standing their ground mainly whilst talking very annoyingly - and then you receiving a health boost from killing them.