Oh, that's the joke! It's already in the game!
The drinking of blood is reclaim.
Getting stronger after every fight is mex capturing.
And the "blood disease" comes from "destroy or be destroyed" mindset, thanks to superweapons.
As to how to discourage fighting? By kindness.
Give the metal to the opponent, so that you wouldn't have much to give.
Getting stronger is dangerous when there are numerous teams.
And the "destroy or be destroyed" mindset falls apart when the enemy consistently refuses to attack anyone, even when given the chance.
But if you can make a mod that adds vampires to the game, I'd love it!