What I've been trying to do on a new playthrough is ensuring the survival of all the random bikers that accompany you on certain missions, mostly just for the added satisfaction of seeing their toughness grow over time rather than losing them over and over.
I know it's impossible to prevent the offscreen deaths of some friendlies in Diamonds in the Rough, but based on my memory you won't lose any previously toughened bikers, so it's alright in my book.
But what I'd like to know if it's possible to do the same in It's War. I even went out of my way to do Bad Cop Drop first to improve the stats of Buck, Earl and Hank to the best they can be before that mission, but somehow, in some way, the latter two always drop dead as if it's scripted when I proceed through the first battle, no matter how aggressively I tackle it. On old playthroughs I have had Buck survive both shootouts, even with just his minimal experience, but never the other two.