Ah pff forget my post
When doing that formula you don't get enough rewards for high amount of kills.
And the difference between low and high ratio gets cancelled by the amount of headshots.

So I am back at the first formula you suggested.
Some things I was thinking about:
- if the kills/deaths/headshot formula go negative round it to 0.
- set in a penalty of -1 for deaths by heavy weapons.
- round the total to zero again if necessarily.
-> What about covert ops? Was thinking about giving half the covert ops xp to make sure whoring with this is useless.